Organic Rose Farming Yields Higher Antioxidant Activity

The global demand for essential oils derived from the oil-bearing rose, Rosa damascena, continues to rise, driven by the expanding fragrance industry and the growing interest in natural health supplements. Bulgaria stands as the leading producer of this specific genotype, particularly within the Kazanlak Rose Valley, where the unique microclimate and soil conditions foster the high-quality blooms required for distillation. Recent scientific inquiry has focused on how agricultural management practices influence the biochemical profile of these flowers, specifically comparing conventional farming methods with certified organic systems. A comprehensive study conducted in Southern Bulgaria aimed to determine whether the type of agricultural system significantly impacts the essential oil composition and the antioxidant activity of industrially cultivated roses.

The investigation took place over a two-year period, from 2019 to 2020, involving six private farms located in the northwest part of the Kazanlak Rose Valley. The study site is situated at an altitude of 400 to 500 meters, characterized by a continental climate with cold, wet winters and cooler summers compared to other regions in Bulgaria. The soil in the valley consists primarily of fluvisols, which are formed by downhill creep and gravity-driven sorting of materials. These soils exhibit an acidic reaction, with pH values ranging between 4.20 and 6.10, and organic matter content varying from 0.86 to 4.03 percent. The selection of farms included three designated as conventional and three certified as organic, allowing for a direct comparison of agricultural practices and their resulting biochemical outcomes.

In the conventional farms, agricultural practices involved soil tillage, mineral fertilization, and foliar feeding with nitrogen, phosphorus, and potassium compounds along with microelements during the vegetation period. Pesticides were also applied to manage pests and diseases. In contrast, the organic farms utilized manure application, biopesticides, and organic fertilizers containing macro and micronutrients. Some organic farms also employed turf surface mulching and drip irrigation to maintain soil moisture and suppress weeds. The primary challenge in organic rose cultivation is the low disease resistance of Rosa damascena, which necessitates the use of Integrated Pest Management strategies. These strategies include landscape modification, habitat management to support natural predators, and rigorous monitoring of pest invasions to minimize the need for chemical interventions.

Essential oil production was determined through steam distillation using a Clevenger-type micro apparatus, with the oil content measured as a percentage by weight. The chemical composition of the essential oil was analyzed using gas chromatography coupled with flame ionization detection and mass spectrometry. Two capillary columns were used to ensure accurate separation of the main terpene alcohols, specifically citronellol and nerol, which have similar retention times. The analysis revealed that while the total essential oil yield was slightly higher in conventional farming, the composition differed significantly. Organic farming produced essential oil with higher concentrations of linalool and geraniol, whereas conventional farming resulted in higher levels of beta-citronellol and nerol. These differences were statistically significant, indicating that the agricultural system plays a crucial role in determining the specific aromatic profile of the rose oil.

Antioxidant activity was evaluated using four reliable methods: the DPPH, ABTS, FRAP, and CUPRAC assays. These methods measure the ability of the rose extracts to scavenge free radicals and reduce metal ions, providing a comprehensive assessment of their antioxidant potential. The results demonstrated that rose extracts from organically grown plants exhibited superior antioxidant activity compared to those from conventionally grown plants. Specifically, the organic farming production showed higher values for DPPH, ABTS, and CUPRAC assays, with averaged data for the two years indicating significantly better performance. The total phenolic and flavonoid contents, which are key contributors to antioxidant activity, were also higher in the organic samples, although the differences were not always statistically significant across all years.

The study also examined the influence of climate conditions, irrigation practices, and plant variety on the essential oil composition and antioxidant activity. Data from the local meteorological station indicated that the 2019 and 2020 periods had varying temperature and precipitation patterns, with 2020 being wetter than 2019. Climate was found to be a significant factor influencing the biosynthesis of certain essential oil components, such as farnesol and tricosane. The drier conditions of 2019 appeared to favor the biosynthesis of secondary metabolites, leading to higher total phenol and DPPH antioxidant activity levels. Irrigation practices did not show a significant impact on the quality of the rose oil or the biosynthesis of secondary metabolites, suggesting that other factors play a more dominant role in determining these characteristics.

The variety of rose also had a notable effect on the essential oil composition. The cultivar Raduga, a cross between Rosa damascena and Rosa gallica, showed higher concentrations of geraniol compared to the native Rosa damascena. This difference was statistically significant, highlighting the importance of genetic factors in determining the biochemical profile of the essential oil. The study underscores the complex interplay between agricultural practices, environmental conditions, and genetic factors in shaping the quality of rose oil and its antioxidant properties. Understanding these interactions is crucial for optimizing production methods to meet the demands of the fragrance and health supplement industries.

The findings of this study have significant implications for the rose oil industry and agricultural practices. The higher antioxidant activity and specific aromatic profile of organically grown roses suggest that organic farming may offer a competitive advantage in the market for high-quality essential oils. Consumers and manufacturers are increasingly seeking natural products with proven health benefits, and the superior antioxidant properties of organic rose extracts align with this trend. However, the higher cost and challenges associated with organic farming, such as the need for additional investments and technologies, must be considered. Farmers and producers must weigh the benefits of organic certification against the economic and logistical demands of sustainable agriculture.

Future research should continue to explore the long-term effects of organic and conventional farming practices on the quality and yield of rose oil. Further studies could investigate the impact of specific agricultural techniques, such as mulching and irrigation, on the biochemical composition of the flowers. Additionally, research into the genetic factors that influence essential oil production could lead to the development of new cultivars with enhanced aromatic and antioxidant properties. By integrating these insights, the industry can work towards more sustainable and efficient production methods that meet the growing demand for high-quality natural products.

In conclusion, the choice between organic and conventional farming systems for oil-bearing roses has a measurable impact on the essential oil composition and antioxidant activity of the flowers. Organic farming, with its emphasis on natural inputs and sustainable practices, yields rose extracts with higher antioxidant potential and a distinct aromatic profile. As the global market for natural health and fragrance products continues to expand, understanding and optimizing these agricultural practices will be essential for maintaining the quality and competitiveness of Bulgarian rose oil in the international market.

Subject of Research: Comparison of essential oil composition and antioxidant activity in organically versus conventionally grown Rosa damascena

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

Article References: 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. BioRisk, 17, 271-285. https://doi.org/10.3897/biorisk.17.77488

Image Credits: AI Generated

DOI: 10.3897/biorisk.17.77488

Keywords: Rosa damascena, Organic farming, Essential oil, Antioxidant activity, Bulgaria, Agricultural practices, Phytochemistry, Sustainable agriculture, Organic, conventional, farming, oil-bearing