BioRisk | 7 27 | 285 (2022) Apeer-reviewed open-access journal

doi: 10.3897/biorisk.1 7.77488 RESEARCH ARTICLE & [3 Ke) Re IS k

https://biorisk.pensoft.net

Organic vs conventional farming of oil-bearing rose:
Effect on essential oil and antioxidant activity

Mima Todorova', Ana Dobreva?, Nadezhda Petkova?,
Neli Grozeva*, Mariya Gerdzhikova’, Petya Veleva®

| Department of Crop Production, Faculty of Agriculture, Trakia University, 6000 Stara Zagora, Bulgaria
2 Institute for Roses and Aromatic Plants Agricultural Academy, 6100 Kazanlak, Bulgaria 3 University of Food
Technologies, Department of Organic Chemistry and Inorganic Chemistry, 26 Maritsa Blvd, 4002, Plovdiv,
Bulgaria 4 Department of Biology and Aquaculture, Faculty of Agriculture, Trakia University, 6000 Stara
Zagora, Bulgaria 5 Department of Crop Production, Faculty of Agriculture, Trakia University, 6000 Stara
Zagora, Bulgaria 6 Department of Agricultural Engineering, Faculty of Agriculture, Trakia University, 6000
Stara Zagora, Bulgaria

Corresponding author: Mima Todorova (minatodor@abv.bg)

Academic editor: Kalina Danova | Received 2 November 2021 | Accepted 30 January 2022 | Published 21 April 2022

Citation: Todorova M, Dobreva A, Petkova N, Grozeva N, Gerdzhikova M, Veleva P (2022) Organic vs
conventional farming of oil-bearing rose: Effect on essential oil and antioxidant activity. In: Chankova S, Peneva V,
Metcheva R, Beltcheva M, Vassilev K, Radeva G, Danova K (Eds) Current trends of ecology. BioRisk 17: 271-285.
https://doi.org/10.3897/biorisk.17.77488

Abstract

The aim of this study was to establish whether the type of the agricultural system has any influence on
the essential oil production and antioxidant activity of industrial cultivated Rosa damascena Mill. in the
Rose valley, Bulgaria. Six private farms from Kazanlak (Rose) Valley, Southern Bulgaria were included in
the study conducted in the period 2019-2020. The first three selected farms are designated within the
conventional farming and the other three are certificated as organic farms. GC/FID and GC/MS analyses
were performed; the contents of total polyphenols and flavonoids in the methanol extracts from rose pet-
als were determined. Additionally, the antioxidant activity of rose extracts was evaluated by four reliable
methods: 2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2’-azino-bis-3-ethylbenzthiazoline-6-sulphonic acid
(ABTS), ferric reducing antioxidant power (FRAP), and cupric reducing antioxidant capacity (CUPRAC)
assays. [he impact of the agricultural system on the essential oil composition and antioxidant activity was
evaluated by ANOVA statistical analysis. The results obtained showed that organic farming produced es-
sential oil with a higher linalool and geraniol content and lower f-citronellol + nerol concentrations than

conventional farming. It was found that organic farming production demonstrated a better antioxidant

Copyright Mima Todorova et al. This is an open access article distributed under the terms of the Creative Commons Attribution License (CC
BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

272. Mima Todorova et al. / BioRisk 17: 271-285 (2022)

activity evaluated by the three DPPH, ABTS, and CUPRAC methods according to the averaged data for
two years, 806.82, 797.66 and 1534.40 mM TE/g dw versus 510.34, 521.94 and 917.48 mM TE/g dw
for CE, respectively, with high statistical significance for the DPPH and ABTS analyses. Consequentially,
the rose extracts from the organic farming accumulated more phenolic compounds that corresponded to

the higher antioxidant potential of the organic roses.

Keywords
cv. Raduga, DPPH, Rosa damascena Mill., rose oil composition, total phenol

Introduction

Globally, the oil-bearing rose, for the production of essential oil, is industrially grown
mainly in Bulgaria, Turkey, Iran, India, Pakistan, China, Morocco, Egypt, France, and
Russia. However, Bulgaria is the leading producer of the main genotype oil-bearing rose
(Rosa damascena Mill.) (Gunes 2005; Kovacheva et al. 2010; Ucar et al. 2017). Accord-
ing to Gunes (2005), 100 kg fresh rose flowers are required to produce approximately
10 g of essential oil. The commercial cultivation of roses in Bulgaria predominantly
includes R. damascena Mill. f. trigintipetala Dieck. (Kazanlak rose) due to its high rose
oil content and chemical composition (Chalova et al. 2017). The observations of re-
cent decades revealed that the cultivar Raduga has spread widely in Bulgarian rose
plantations (Kovacheva et al. 2010). It is a cross pollination result of Rosa damascena
Mill. X Rosa gallica L., with high productiveness and essential oil content. Recently,
interest in rose oil production has been growing not only due to its perfuming effects
but also because of the wide range of biochemical reactions, such as an analgesic, hyp-
notic, antispasmodic, anti-inflammatory and anticonvulsant, which the rose flowers
exhibit. (Baydar and Baydar 2013; Kumar et al. 2013; Mahboubi 2016) On the other
hand, there is a real interest in organic crop production, particularly with aromatic
and medical plants. Organic agriculture is an alternative cultivation model involving
the agricultural practice without chemical additives. This cultivation method is de-
signed to encourage respect towards the biological cycles of the production system to
maintain and to increase soil fertility, to minimise any form of pollution, to avoid the
use of synthetic fertilizers and pesticides, to maintain the genetic diversity, to consider
the wide social and ecological impact of the food production system and to produce
good quality foods in sufficient quantities. (Giuseppina et al. 2011). The choice of
organic production of an essential oil crop in comparison with the conventional one is
frequently registered as expensive and more challenging for agricultural producers, but
the results are of particular importance for improved lifestyle, health, and longevity.
Thus, the production of organic rose flowers and oil requires the application of new ag-
ricultural practices, which require additional investments and technologies in order for
the production to be certified as organic and cost effective. One of the main challenges
in rose oil organic cultivation is the fact that R. damascena exhibits low disease resist-

Organic vs conventional farming of oil-bearing rose 273

ance to major diseases and pests (Kovacheva et al. 2010). In this regard, the Integrated
Pest Management (IPM) has a dominant role in organic rose oil cultivation. The most
commonly applied IPM approaches include designing or redesigning the landscape,
modifying the habitat to reduce the pest’s resources and increase the habitats for natural
predators, changing cultural methods such as cultivation, weeding, mulching as well
as increasing inspections and tight monitoring of pest invasion (Chalova et al. 2017).
Nunes and Miguel (2017) discussed the influence of several factors on the chemical
composition of Damask rose oil and concluded that agricultural practices, important
for essential oil productiveness and biochemical composition were mainly: method of
propagation, time of the day of flower harvesting - air temperature, relative humidity,
intensity of sunlight, flower stages, day period of harvesting, harvest procedures, time
and level of pruning, storage of plant material, and method of distillation. Erdal and
Munduz (2017) reported that the nutrient concentrations of the leaves from conven-
tional gardens of R. damascena Mill were significantly higher than the organic ones,
particularly for the nitrogen, manganese, and zinc content. Similarly, the flower nutri-
ent concentrations of conventional gardens were higher for all examined nutrients, and
the differences between organic and conventional gardens for the nitrogen, potassium,
calcium, and iron concentrations were significant. The application of the anti-gibberel-
lic, Paclobutrazol (PP333), combined with supplied nitrogen as NH,-N and NO,-N in
appropriate amounts, and the micronutrients Mn’» Zn** and Cu” enhanced the flower
bud formation and flowering as well as the rose oil yield with higher percentage of cit-
ronellol. Ucar et al (2017) reported the significant effect of different irrigation amounts
and nitrogen doses 160 kg ha™' and 240 kg ha"! on the flower yield and rose oil yield for
2011 and 2012 (P < 0.01), but it was not established to be significant for the first year
of investigation 2010. The effect of the cultivation practices on the fruit quality and
antioxidant capacity was evaluated in many studies. (Wang et al. 2008) ‘There is a small
number of studies investigating the effects of agricultural practices on the secondary
metabolites in medicinal and aromatic plants (Malik et al. 2011). Our primary investi-
gations showed that the highest values of total phenols and flavonoids are found in the
rosewater extract from organically grown plants: 47.09£2.89 mg GAE/g dry weight
and 6.87+3.00 mg QE/g dry weight, respectively (Petkova et al. 2020). The highest
radical scavenging activity was demonstrated by the extracts from organic plantations,
while the metal-reducing assays showed higher antioxidant potential in the extracts
from conventionally grown roses. Since many of the bioactive secondary metabolites
produced by medical plants have ecological roles in promoting plant survival under a
range of environmental conditions (Briskin 2000), Malik et al (2011) confirmed that
the production of secondary metabolites within the medicinal and aromatic plants is
under diverse physiological, biochemical, metabolic and genetic regulations and can be
manipulated by alterations in the growing conditions. The aim of our study was to con-
tinue the investigation in that field in order to answer clearly whether the type of the
agricultural system has any influence on essential oil production and the antioxidant
activity of industrial cultivated R. damascena in the Rose valley.

274 Mima Todorova et al. / BioRisk 17: 271-285 (2022)

Materials and methods

Location and site description

The field study was conducted in private farms, located in the northwest part of the
Kazanlak Rose valley, Bulgaria, in the two-year period of 2019-2020. The valley is
situated at 400-500 m altitude, in the middle of the country between the Balkan
range in the north and Sredna Gora mountain to the south. ‘The climate is continental,
the winters are generally cold and wet, and the summers cooler than in other parts of
Bulgaria. January is the coldest month of the year with a -1.1 °C average temperature.
July is the warmest month in Kazanlak with an average temperature of 21.2 °C. Spring
in Kazanlak has the feel of winter, with late snowfalls. The annual precipitation rates
range from 500 to 650 mm in the Kazanlak valley, with heaviest precipitation between
April and June (Sobotkova and Ross 2018). Data about the climatic conditions of the
studied years were provided from the local meteorological station, situated in Kazan-
lak. The monthly distribution of the average temperatures and rainfalls, compared to
the 100-year average rate are presented in Figs 1, 2, respectively.

The field study was conducted in six private farms, as three of the oil rose private
plantations are certified as organic farms whereas they apply an organic agricultural
system and the rest of them are designated within the conventional farming. The
farms are located close to each other and the dominant soil type is fluvisols. Fluvisols
(Deluvial soils) are formed by downhill creep, where the sorting of materials comes
about through gravity. Creep is the slow movement of soil masses down slopes that are

25 -
= 2019
20 = 2020
= Norms
15
i? 2]
=
ea
S 10
rm)
iB)
Pa
y
Q 5
0 — —| = = — p— | /— — = = —
I Il It IV V VI «#«GVIE €«€CVI OLX »,4 XI XII
5

Months
Figure |. The average monthly temperatures (°C) for Kazanlak valley in 2019/2020.

Organic vs conventional farming of oil-bearing rose O75

400 -

350 - a= Norms

Column of water, mm

0 “T T T r T T T T T ~T
I il ii IV Vv VI «OVIT «VI OX X XI XII

Months

Figure 2. The average monthly rainfall (mm) for Kazanlak valley in 2019/2020.

usually steep. The process takes place in response to gravity where there is a pronounced
water saturation (Shishkov and Kolev 2014). The soils in the region have ochric and
nondiagnostic features, typical of fluvisols. The soil samples in all six arable areas were
characterized by acid reaction, typical for that soil. The range of values of pH (H,O)
was between 4.20 and 6.10. The soil organic matter (OM) content varied between
low and high content with values from 0.86 to 4.03%, where the mean OM, % value
was 2.80. More detailed information about the soil characteristics was reported by
Todorova et al. (2020).

Agricultural practices in the studied farms

Detailed characterization of the agricultural practices of the studied farms is presented
in Table 1.

Farm 1 is characterized as typical conventional farming with soil tillage, mineral
fertilization, foliar feeding with NPK + microelements during vegetation. ‘The soil till-
age included 3—4 hoeing with a cultivator between the rows.

Farms 2 and 3 are conventional with combined good agricultural practices, in our
case - turf surface as mulching, drip irrigation, mineral fertilization, foliar feeding with
NPK + microelements during vegetation.

Farm 4 is certified as organic farming with manure fertilization 2—3 t/dka (20-30 t/
ha), applied every 3—4 years before vegetation. Before and after flowering — several times
foliar application of organic fertilizer containing macro-, micronutrients, and amino
acids. Only soil tillage was carried out to control weeds. ‘The soil tillage included 3-4
hoeing with a cultivator or manually between the rows, with biopesticides application.

2/6 Mima Todorova et al. / BioRisk 17: 271-285 (2022)

Table |. Farming system, geographical data, variety with general agricultural practices in the studied farms.

Farm’s Area GPS Variety Agricultural practices Drip
number coordinates irrigation
Conventional Farming (CF)
01 Koprinka 42°38'10.74"N, R. x damascena f. Soil tillage, mineral fertilization, foliar feeding with -
25°19'29.496"E _trigintipetala Dieck | NPK + microelements during vegetation, pesticides
02 Damascena 1 42°40'11.6"N, R. x damascena f. Turf surface as mulching, mineral fertilization, yes
25°11 50 E trigintipetala Dieck foliar feeding with NPK + microelements during
vegetation, pesticides
03 Damascena 2 42°40'6.60"N, R. x damascena f. Turf surface as mulching, mineral fertilization, yes
25°11'53.40"E trigintipetala Dieck foliar feeding with NPK + microelements during
vegetation, pesticides

Organic Farming (OF)
04 Yasenovo 42°41'36.0"N, R. x damascena f. Soil tillage, manure application, bio pesticides -
25°16'39.8"E trigintipetala Dieck
05 Asen 42°38'35.8"N, cv. Raduga Rosa Turf surface as mulching, manure application, bio yes
25°10'30.0"E damascena x Rosa gallica pesticides
06 Skobelevo 42°40'16.5"N, cv. Raduga Rosa Turf surface as mulching, manure application, bio yes
25°10'36.5"E damascena x Rosa gallica pesticides

Farms 5 and 6 are also certified as organic farming, with manure fertilization, foliar
application of organic fertilizer containing macro-, micronutrients, and amino acids,
with a turf surface as mulching between the rows and drip irrigation.

Plant material and sampling

We surveyed farms growing oil-bearing roses - R. damascena Mill. f. trigintipetala Dieck
and cultivar Raduga [(Rosa damascena Mill. x Rosa gallica subsp. Eryosyla Kell var.
Austriaca Br.) x Rosa gallica L.] (Nazarenko 1983). The harvest time for rose oil yield is
early in the morning, between 6 and 11 a.m., to avoid temperature increase during the
day, which negatively affects the yield and the quality of the rose oil (Chalova 2017).
The samples of rose flowers were picked up in the morning (6—8 a.m.) within a day at
the beginning of June 2019 and 2020. Three samples were randomly taken from each
individual field, and each of them was collected from 40 different rose bushes. Similar
experimental designs were presented by Vagn et al. (2000) for onion and peas and by
Tuncay and Bostan (2010) for apricot under organic and conventional cultivation.
Each sample of rose flowers (1000 g) was split into two parts. The first was used for
distillation and essential oil production. The second sample of rose flowers was used
for biochemical analysis.

Distillation and essential oil production

The essential oil content in the blossoms was determined after steam distillation in the
Clevenger-type micro apparatus. The essential oil was measured to the graduated part
of the apparatus in milliliters and was calculated as a percentage by volume (v/w). For
higher accuracy, a relative density recalculation was made and was presented as a per-

Organic vs conventional farming of oil-bearing rose 277

centage by weight (w/w). After collection, the oil was treated with anhydrous Na,SO,
and stored in tightly closed vials at 4 °C till analysis. The analysis was performed on
an Agilent 7820A GC System coupled with a flame ionization detector and 5977B
MS detector. The protocol was made according to ISO 9842 for gas chromatograph-
ic analysis of rose oil. Two capillary columns: non-polar EconoCap'™ EC™ (30 m
x 0.32 mm ID, 0.25 um film thickness) and polar HP-20M (50 m x 0.32 mm ID,
0.30 um film thickness) were used. The first one was operated with an oven program
from 80 °C (2.5 min held) to 320 °C at a rate of 10 °C/min; with 10 min held at
the final temperature was applied. Hydrogen (99.999%) was used as a carrier gas at a
constant flow rate of 20 ml/min. The split ratio was 1:10, the inlet temperature was set
to 250 °C and the FID temperature was set to 300 °C. The non-polar column reveals
a much richer spectrum of compounds and better presentation of paraffins, but it is
not suitable for dividing the main terpene alcohols citronellol and nerol. They have
very similar retention times and could not be split and calculated. For this reason the
polar column was used for better separation. Due to the character of the HP-20M,
the oven temperature program was the following: 65 °C for 0 min, then 2 °C/min to
220 °C for 10 min.

The GC/MS analysis was performed under all conditions, described above.

The ingredients were quantified by the area of FID peaks without any correction
factor. The oil constituents were identified by their mass spectra, matching with the
NIST and MS library, as well as whenever possible, the authentic substances were used.

Extracts preparation

Rose petals were subject to extraction in duplicate with 80% methanol in 1:15 solid
to solvent ratio. The extraction was conducted in an ultrasonic bath (SIEL, Gabrovo,
Bulgaria, 35 kHz, and 300 W) for 20 mins, at 65 °C. The combined extracts were used

for further analysis.

Total phenolic contents

The total phenolic content was measured using a Folin-Ciocalteu reagent with slight
modification (Ivanov et al. 2014).

The total flavonoids content

The total flavonoids content was analyzed using Al(NO,), reagent (Kivrak et al. 2009).

2,2-diphenyl-|-picrylhydrazyl (DPPH) assay

The rose petal water extract (0.15 mL) was mixed with 2.85 mL 0.1 mM methanol
solution DPPH. After 15 min at 37 °C, the reduction of absorbance was measured at
517 nm against methanol used as a blank sample (Ivanov et al. 2014).

278 Mima Todorova et al. / BioRisk 17: 271-285 (2022)

2,2°-azino-bi’s-3-ethylbenzthiazoline-6-sulphonic acid (ABTS) assay

The rose petal extract (0.15 mL) was mixed with 2.85 ml of the ABTS solution. After
15 min at 37 °C in darkness, the absorbance was measured at 734 nm (Ivanov et al. 2014).

Ferric reducing antioxidant power (FRAP) assay

The assay was performed according to Benzie and Strain (1996).

Cupric reducing antioxidant capacity (CuPRAC) assay

The rose petal extract (0.1 mL) was mixed with 1 mL CuCl2.2H2O, 1 mL Neocu-
proine (7.5 mL in methanol), 1 mL 0.1 M ammonium acetate buffer and 1 mL dis-
tilled water. After 20 min at 50 °C, the absorbance was measured at 450 nm (Ivanov et
al. 2014). All results for the antioxidant activity were expressed as mMTE/g.

Statistical analysis

The data were expressed as a meantstandard deviation (SD) from three replicates
for each sample. All the results from the determination of antioxidant activity were
performed in triplicates and expressed as mM Trolox equivalents (mM TE) by dry
weight. To establish the influence of the agricultural practices in the studied farms on
the essential rose oil composition and antioxidant activity, ANOVA statistical analysis
was performed. The significant differences were tested and the P values < 0.05 were
considered statistically significant. The impact of the factors was evaluated via the Co-
efficients of determination R’*. The IBM SPSS Statistics 26.0, Copyright 1989, 2019

statistical package was used to process the data.

Results and discussion

Essential oil composition

The climate data for the 2019-2020 period showed that the temperatures were much
higher than the average rates for the winter season (especially 2019). This is the dor-
mancy period for the plants. During the spring months, the temperatures were normal
and higher in June, particularly in 2019. Regarding precipitation, it is obvious that in
both years they were below normal. The second year of the study is characterized as
wetter with more rainfall than in 2019, especially during the spring.

The chemical composition of the essential oil of rose flowers under conventionally
and organically grown roses is presented in Table 2. According to the averaged data for
the two periods, the productiveness of essential oil, % obtained in conventional farm-

ing (CF) was 0.04% higher than the organic system (OF) - 0.03%, with insignificant

Organic vs conventional farming of oil-bearing rose 279

Table 2. Biochemical composition of the essential oil of rose flowers under conventionally and organi-

cally grown roses for the two years period of study.

Type of farming Conventional farming - CF Organic farming - OF R
Biochemical component min max average SD min max average SD
Rose oil,% 0.03 0.05 0.04" 0.01 0.02 0.05 0.03" 0.01 0.229
Ethanol 0.00 0.92 0.19" 0.36 0.01 0.92 221579 0.31 0.025
Linalool 0.38 0.71 0.54? 0.11 0.52 0.93 0.61" 0.22 0.569
cis —Rose oxide 0.15 0.27 0.22? 0.05 0.00 0.27 0.16 0.10 0.521
trans —Rose oxide 0.08 0.14 0.12? 0.02 0.00 0.14 0.08 0.05 0.532
Phenylethyl alcohol 0.33 1.33 0.83" 0.37 0.34 1.33 0.80" 0.34 0.000
8-Citronellol and Nerol 25.48 33.60 29.47? 3.18 17.86 33.60 25.08 7.91 0.450
Geraniol 23elc 26.13 24.33? 1.18 20.91 35.81 25.42? 8.03 0.427
Eugenol 0.38 1.35 0.70" 0.35 0.00 1.35 0.56" 0.46 0.185
Methyleugenol 0.46 0.72 0.60 0.10 0.00 1.32 0.50" 0.36 0.055
Heptadecane (C,,) 0.85 2.47 1.96" 0.60 0.98 2.69 1.83" 0.68 0.000
Farnesol 0.19 3.37 M51 1.43 0.32 3.37 1.59" 1.32 0.003
Nonadecene (C,,.,) + Nonadecane (C,,) 14.37 18.62 17.293 1.65 11.36 18.62 15.09? 4.30 0.367
Eicosane (C,) 0.98 1.76 1.33" 0.27 0.52 1.77 1.11" 0.46 0.261
Heneicosane (C,,) 4.56 8.56 6.008 1.37 2.71 10.14 5.43" 2.26 0.053
Tricosane (C,,) 0.90 2.06 1.36" 0.43 1.06 3.01 1.50" 0.70 0.139
Pentacosane (C,,) 0.27 0.80 0.50" 0.19 0.36 1.16 0.56" 0.28 0.118
Heptacosane (C,,) 0.16 0.64 0.38" 0.16 0.19 0.92 0.38" 0.21 0.013

a,a Same superscripts within the same row represent significant differences at the level of significance P < 0.05; ns — not significant differ-
ences (P > 0.05); R2 — Coefficients of determination based on observed means.

difference. Statistically significant differences were found between the average values of
the main components of essential oil composition such as geraniol, 8-citronellol + nerol,
9) + nonadecane (C,,). The
content of geraniol, 8-citronellol and neroll varied within the following range: geraniol
(23.11-26.13%), 8-citronellol and neroll (25.48—33.60%) for CF and (20.91—35.81%),
(17.86-33.60%) for OE (Table 2). The hydrocarbons are presented by aliphatic alkanes
and alkenes. The major of them is nonadecane (C,,,) + (C,,) with values between (14.37—
18.62%) for CF and (11.36—18.62%) for OF the next one is heneicosane (C,,H,,), var-
ied from (4.56% to 8.56%) for CE, and (2.71 to 10.14%) for OF The other saturated

hydrocarbons (tricosane, pentacosane, and heptacosane) do not show a certain trend and

linalool, cis-rose oxide, trans-rose oxide, and nonadecene (C

move relatively within an equal range. The phenylpropane compounds are represented
by phenylethyl alcohol, eugenol and methyleugenol. ‘The first one is most abundant in a
native flower odor, but in the essential oil, its quantity is minor (Dobreva 2011; Rusanov
et al. 2011; Erbas and Baydar 2016). Due to its high water solubility, this substance is
carried off with the distillation waters. It is limited in the international standard with
less than 3.5%. In our study, it varies within the narrow range from 0.33 to 1.33% for
CF and 0.34 to 1.33% for OE The methyleugenol is an odor contributor, but it is not
desired above a certain concentration in the essential oils due to potential cancer and al-
lergic effects on human health (Johnson et al. 2000). ‘The rose oil contains methyleugenol
in percentages up to 5.0%, especially if the rose flowers are fermented before processing.
This compound is limited and subject to monitoring. For the two-year period, the levels

are relatively low: from (0.46 to 0.72%) for CF and from (0.00—1.32%) for OE The

280 Mima Todorova et al. / BioRisk 17: 271-285 (2022)

results of the statistical analysis showed an influence on the essential oil composition in
our study case. The coefficients of determination (R’) vary within the range from 0.367
to 0.569, thus, the influence of the type of rose oil cultivation varied from 36.7 to 56.9%.
A significant difference was not found for the other components of the biochemical com-
position of the essential oil, and the coefficients of determination (R’) varied within very
low limits. On the basis of the results obtained, the organic farming produced essential
oil with higher linalool and geraniol content and lower $-citronellol and nerol concentra-
tions, whereas the essential oil of CF is characterized by higher 8-citronellol and nerol
concentrations and lower linalool and geraniol content. Similar results were obtained by
Kumar et al (2017), the authors reported more flower yield plant-', number of flowers
plant, ' and flower yield ha"! and a higher percentage of citronellol+nerol with an appli-
cation of 120:40:90 kg NPK ha‘. The authors discussed that the ratio citronellol+nerol/
geraniol is higher for fertilized plots in comparison with manure plots. In our study the
ratio citronellol+nerol/geraniol was also bigger 1.21 for CF than OF - 0,98.

Antioxidant activity of the rose flower

The total phenols, total flavonoids, and antioxidant activity in methanol extracts from
conventionally and organically grown roses are presented in Table 3.

The phenolic compounds, even if not directly related to the food nutritional qual-
ity, have been receiving increasing attention as a result of their specific biological activ-

Table 3. The total phenols, total flavonoids and antioxidant activity in methanol extracts from conven-

tionally and organically grown roses.

Compound,% Region Year Total Total flavo- Antioxidant activity, mM TE/g
phenols, mg noids, mg DPPH ABTS FRAP CUPRAC
GAE/gdw QE/g dw
Conventional Koprinka 2019 49.01+0.22 11.0740.23 524.32+39.89 522.74465.06 3235.01+27.85 1713.834147.19
farming Koprinka 2020 40.60£13.30 9.3841.12 596.614128.1 544.50+111.18 955.50+333.31 456.79+52.22
Damas1 2019 41.14+0.23 11.4941.44 509.57434.58 571.33£96.56 2309.14£227.49 1128.144£77.45
Damas1 2020 39.50£7.3 11.13£1.30 639.64+127.62 578.43+77.21 1602.74£316.61 723.13£193.31
Damas2 2019 41.74+0.07 11.59+0.64 476.75+41.83 607.67£79.99 2744.97+189.04 1176.25+145.31
Damas2 2020 23.143.2 7.4640.56 315.143+89.74 306.99+82.78 1062.2+326.452 306.76£44.27
min 23.10 7.46 315.14 306.99 955.50 306.76
max 49.01 Tes) 639.64 607.67 3235.01 1713.83
average 39.18 10.35 " 510.34 * 521.94 * 1984.93 917.48"
SD 8.58 1.63 112.77 109.26 927.65 523.16
Organic farming Yasenovo 2019 63.45£0.05 12.3640.50 1033.06430.57 793.724£63.72 3141.96£29.02 2687.07+121.83
Yasenovo 2020 36.30+4.9 8.8942.27 592.86464.63 604.33£78.95 1418.70£362.67 537.34£107.42
Asen 2019 73.2340.99 11.3240.68 839.96412.47 1033.31+84.04 746.41490.16 2658.17+242.94
Asen 2020 41.8+12.8 13.0242.46 675.694179.13 676.234178.20 1301.94609.73 687.46+169.86
Skobelevo 2019 69.8344.58 11.5541.0 754.32429.86 1026.13421.60 721.49+44.06 1760.29+112.99
Skobelevo 2020 41.343.3 13.03£1.56 945.04+326.25 652.21+45.17 3648.341951.29 876.06£107.71
min 36.30 8.89 592.86 604.33 721.49 537.34
max 73.23 13.03 1033.06 1033.31 3648.30 2687.07
average 54.32" 11.70" 806.82 * 797.66 * 1829.79 ™ 1534.40
SD 16.32 1.55 165.60 190.27 1255.27 978.51
R 0.288 0.176 0.568 0.486 0.006 0.156

a,a Same superscripts within the same column represent significant differences at the level of significance P < 0.05; ns — not significant

differences (P > 0.05); R2 — Coefficients of determination based on observed means.

Organic vs conventional farming of oil-bearing rose 281

ity. Higher values of the total phenols were found in the methanol extract of rose petals
from OF between (36.30—73.23) mg GAE/g dw, with a mean value of 54.32 mg GAE/g
dw and a lower concentration for CF between (23.10—49.01) mg GAE/g dw with a
mean value of 39.18 mg GAE/g. ‘The values of total flavonoids varied between 8.89 and
13.03 mg QE/g dw with a mean value of 11.70 mg QE/g dw for OF and (7.46-11.59)
QE/g dw with a mean value of 10.35 QE/g dw for CE An interaction was found between
the impact of the agricultural system and annual conditions in the study period on the
total phenol and total flavonoids content, but a statistically significant difference was
not found with regards to the agricultural system. The antioxidant activity of the rose
petal extracts was evaluated by four methods based on the different mechanisms (DPPH,
ABTS, FRAP, and CUPRAC). It was found that organic farming production (Table 3)
demonstrated the best radical scavenging activity evaluated by the three DPPH, ABTS,
and CUPRAC methods according to the averaged data for two years, namely 806.82,
797.66 and 1534.40 mM TE/g dw for OF versus 510.34, 521.94 and 917.48 mM TE/g
dw for CF with high statistical significance for the DPPH and ABTS analyses. ‘The coef-
ficient of determination (R’) showed influence of the agricultural system type on the oil
bearing rose cultivation with more than 0.49% on antioxidant activity in oil rose flower.
The authors’ team of Wang et al. (2008) also reported significantly higher total phenolics,
total anthocyanins, and antioxidant activity in blueberry fruit grown from organic culture
than fruit from conventional farming. The investigation of Taie et al. (2010) with basil
plants also indicated that organic fertilization can yield a significant increase in antioxi-
dant activity, anti-cancer activity, phenolics, and flavonoids of the culinary herbal plant.

The impact of climate conditions in 2019 and 2020, irrigation practice and the
variety types on the essential oil composition and the antioxidant activity of rose petals
was also studied. The results are presented in Table 4.

According to Dobreva and Angelova (2011), the greatest influence on the biosyn-
thesis of the essential oil is attributed to temperature, humidity, and light intensity,
whereas the air humidity is associated with an increased production of the rose flowers
and rose oil content. Therefore, the second year 2020 would be more favorable for the
growth of the oil-bearing rose and the production of essential oil in the study region.
As can be seen from the data presented in Table 4, the productiveness of essential oil
from the studied private farms was greater in 2020 by 0.04% than it had been in 2019,
without a statistical significance. Results of the statistical analysis showed that climate
in the period under study was a factor influencing essential oil composition. Statistically
significant differences were found between the average values of the components such as
farnesol, tricosane, pentacosane and heptacosane. The coefficients of determination (R’)
varied within the range from 0.35 to 0.97, thus, the influence of the climate conditions
on these components varied from 35% to 97%. A statistically significant difference was
also found with regards to the total phenols and the DPPH antioxidant activity, whereas
the drier year of 2019 was more favorable for biosynthesis of second metabolites. ‘This
confirmed that the contents of polyphenolics and antioxidants in the rose petals (R’
= 0.47; 0.65) are strongly influenced by the environment, e.g. the geographical and
edaphic factors, as previously described by Ginova et al. (2013). Any impact of the ir-

282 Mima Todorova et al. / BioRisk 17: 271-285 (2022)

rigation practice on the rose oil quality and biosynthesis of second metabolites was not
found. According to Ucar et al (2017) irrigation, as an agronomic practice has a signifi-
cant effect mainly on the oil bearing flower yield. A statistically significant difference of
the essential oil composition was found between the R. damascena and cv. Raduga for
the main components such as geraniol, 8-citronellol and neroll and eugenol. The first
thing that stands out is the relationship between the most abundant terpene alcohols
— for Raduga the dominant is geraniol (32.36—35.81%) and lower for R. damascena,
between (20.91—27.24%) whereas the coefficient of determination is R? = 0.89.

Table 4. Impact of the climate condition in 2019 and 2020 years, irrigation practice and variety on the

rose oil composition and the antioxidant activity of rose petals.

Biochemical component of — min max mean SD min max mean SD R
rose oil/rose flower
2019 Year 2020 Year
Essential oil, % 0.02 0.04 0.03. 0.01 0.03 0.05 0.04 0.00 0.01
Farnesol 0.19 3.37 0.28, 0.67 2.43 3.37 2.88, 0.34 0.97
Tricosane (C,,) 1.30 3.01 2.09. 0.68 0.90 1.31 1.18, 0.17 0.54
Pentacosane (C,,) 0.45 1.16 0.77, 0.30 0.27 0.53 0.42. 0.98 0.44
Heptacosane (C,,) 0.26 0.92 0.52, 0.24 0.16 0.38 0.28, 0.08 0.35
Total phenols, mg GAE/gdw = 41.14 73.23 56.40. 14.25 23.10 41.80 37.10, 7.13 0.47
CUPRAC,mM TE/g 1128.14 2687.14 1853.96, 686.34 306.76 876.06 597.92, 204.66 0.65
Irrigation Non irrigation
Methyleugenol 0.00 0.67 ie SB 0.27 0.67 1.32 0.92, 0.30 0.56
Heptadecane (C,.) 1.76 2.69 2.22" 0.29 0.85 2.36 1-408 0.68 0.47
R. Damascena cv. Raduga
Linalool 0.38 0.83 0.57, 0.14 0.81 0.93 0.87 | 0.56 0.62
cis —Rose oxide 0.15 0.27 0.22 0.43 0.00 0.04 0.02 | 0.21 0.88
trans —Rose oxide 0.08 0.14 0.12, 0.23 0.00 0.03 0.01, 0.02 0.87
8-Citronellol and Nerol 25.48 33.60 29.29 | 3.05 17.86 20.02 18.80 | 0.96 0.81
Geraniol 20.91 27.24 24.27 | 1.97 32.36 35.81 34.46 | 1.64 0.89
Methyleugenol 0.46 1.32 0.74, 0.28 0.00 0.14 0.06 , 0.07 0.68
Eicosane (C,,) 0.98 1.77 1.35, 0.30 0.52 0.89 0.66 , 0.17 0.64
ABTS, mM TE/g 306.99 793.70 566.21, 133.45 652.21 1033.31 846.97. 211.27 0.45

a,a Same superscripts within the same column represent significant differences at the level of significance P < 0.05; R2 — Coefficients of
determination based on observed means, SD-Standard deviation.

Conclusion

The conventional or organic agricultural type of system is a question of choice for
every farmer, based on the benefits and challenges in the agricultural sector. In the
medical plants cultivation, including oil bearing rose production, the choice of the
system and the application of agricultural practices could have an enormous effect on
the quality of cosmetic rose products and food supplements. Our results show that the
application of combined eco-friendly agricultural practices in organic private farms in
R. damascena cultivation gives a better quality of the rose flowers with higher values of
antioxidant activity in comparison with the conventional agricultural system.

Organic vs conventional farming of oil-bearing rose 283

Acknowledgements

This work was supported by the Bulgarian Ministry of Education and Science under
the National Research Programme “Healthy Foods for a Strong Bio-Economy and
Quality of Life” approved by DCM N° 577/17.08.2018.

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