Screening of Flowers Essential Oil and Hexane Extract of Rheum ribes L. from Iran- Chemical Composition, Antioxidant and Antimicrobial Activities

The hexane extract of the flowers of Rheum ribes L. which was collected from north western Iran, was obtained by Soxhlet apparatus and the essential oil composition was obtained by hydro distillation and analyzed by using GC-GC/MS. The extract from the flowers was characterized by a high amount of unsaturated fatty acids (UFA) (66.0%) and some of long chain hydrocarbon compounds. The main components of the hexane extract were 9-octadecenoic acid(ω-9) (42.8%), 9, 12- octadecadienoic acid (linoleic acid or ω - 6) (19.6%), hexadecanoic acid, (palmitic acid) (8.6%), 1,2 benzenedicarboxylic acid diisooctyl (5.7%), dodecane (3.7%) and γ- linolenic acid (3.6%). The hexane extract from Rheum ribes flowers detected as an important source of ω-6 and ω-9 compounds. This study reveals that the flowers of this plant are attractive sources of oily components, especially the essential ones, as well as of effective natural sources of unsaturated fatty acids. Twenty three compounds representing 97.5% of the distilled oil of R. ribes flowers were identified, among them germacrene-d (22.3%), α pinene (13.5%), terpinolene (12.4%), p-cymene (10.6%), bicyclogermacrene (9.6%) and limonene 8.6%) were the major constituents. The antimicrobial activity of the essential oil and hexane extract were determined against some bacteria and both samples had a moderate effect on the some Gram-positive and Gram-negative bacteria. The antioxidant activity of the extract and essential oil were evaluated by DPPH method. The results indicate that hexane extract of this plant flowers possess considerable antioxidant activity.