Biological effects of essential oils and extracts
Shahla Hosseini; Sajjad Atashi
Abstract
Background and Objective: Viola odorata L. and Hymenocrater longiflorus Benth., two wild medicinal plants from the Kosalan region of Kurdistan Province, are recognized for their promising health-related effects. Viola is the largest genus in the Violaceae family, with 30 out of its ...
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Background and Objective: Viola odorata L. and Hymenocrater longiflorus Benth., two wild medicinal plants from the Kosalan region of Kurdistan Province, are recognized for their promising health-related effects. Viola is the largest genus in the Violaceae family, with 30 out of its 525-600 species identified in Iran. V. odorata (sweet violet) is widely used in the perfume industry and contains secondary metabolites with anti-inflammatory, sedative, detoxifying, and antiviral properties. Its various plant parts are known for medicinal uses, and local ecotypes have been documented. Hymenocrater, from the Lamiaceae family, includes 24 species found in Iran and neighboring countries; nine are reported in Iran, and H. longiflorus has ornamental and medicinal properties. Located in northwestern Iran, including Kosalan, H. longiflorus has no dedicated medicinal studies, although the genus exhibits sedative, anti-inflammatory, antispasmodic, and antipyretic activities. Both families are valued for their high antioxidant and phenolic content, driving pharmaceutical interest. This study focuses on assessing the antioxidant capacity, phenolic and flavonoid composition, and antibacterial properties of flower and leaf methanolic extracts from both plants, to highlight their medicinal potential.
Methodology: Plant samples were collected from the Kosalan region, and herbarium samples were prepared. Extraction from the aerial parts (flowers and leaves) was performed using methanol as a solvent. Antioxidant capacity was measured using the Ferric Reducing Antioxidant Power (FRAP) method and DPPH radical activity at different extract concentrations. Additionally, phenolic content was measured using the Folin-Ciocalteu method, and flavonoid content was assessed using the aluminum chloride colorimetric method. The antibacterial properties of the samples were evaluated using disk diffusion and tube dilution methods against Gram-positive and Gram-negative bacterial strains.
Results: According to the results, the flowers of H. longiflorus exhibited the highest reducing power and free radical inhibition (IC50 = 851.4 µg.ml-1) compared to the standard Trolox (IC50 = 612.35 µg.ml-1). The leaves of V. odorata contained the highest amount of flavonoids, with 58.21 mg of quercetin per gram of dry extract, while the flowers of this species had the lowest amount of flavonoids (3.37 mg QE/Ex). The phenolic content of the samples ranged from 30 to 33 mg of gallic acid per gram of extract. Antimicrobial tests indicated that the flower extract of V. odorata had no effect on the proliferation of the strains, but its leaves created a 7 mm zone of inhibition at a concentration of 200 µg/mL against E. coli. The leaves of H. longiflorus exhibited a significant inhibitory effect only on S. aureus, while its flowers demonstrated inhibition against S. aureus at all concentrations tested (18 mm). This species also inhibited the growth of E. coli at a concentration of 200 µg.ml-1 (13 mm). Results from the tube dilution tests indicated a MIC of 25 µg.ml-1 and MBC of 50 µg.ml-1 for the flowers and leaves of H. longiflorus against S. aureus, and a MIC of 200 µg.ml-1 for E. coli. The flower extract of V. odorata was ineffective against both strains, while its leaf extract confirmed a MIC of 200 µg/ml. The results of this test were consistent with the antibiogram test. GC analysis confirmed the presence of terpenoids, sesquiterpenoids, alkaloids, sugars, and esters in these species, suggesting potential antidiabetic and anticancer properties.
Conclusion: This study concludes that the flower methanolic extract of H. longiflorous has significant antioxidant and antimicrobial activities. These findings highlight the potential of this species as a source of natural antioxidants and antimicrobial agents, which could be utilized in food preservation, pharmaceuticals, and natural product-based industries. Further research is required to isolate and identify the specific bioactive compounds responsible for these effects.
