New prenylated flavonoids from the leaves of Dodonea viscosa native to the Sultanate of Oman

Traditionally, in Oman, the whole plant is used to treat the body, including treatment of anaemia, arthritis and skin inflammation. Crude extracts were prepared from the leaves of Dodonea viscosa (D. viscosa) using different polarities of solvents to isolate flavonoid compounds from the highest activity crude extract of the selected plant species collected from AL-Jabal AL Akhdar, Nizwa. The plant samples were collected, processed and extracted with methanol using a hot extraction method. The prepared crude extract was dissolved in water and successively fractioned with different polarities of solvents to produce hexane, chloroform, ethyl acetate, butanol and water crude extracts. The chloroform crude extract was used for the isolation of flavonoid compounds by thin layer chromatography, column chromatography and preparative thin layer chromatography. The free radical scavenging activity of the isolated pure compound and the different polarities of crude extracts were determined using the 1,1-diphenyl-2-picrylhydrazyl method.

The highest antioxidant activity in crude extracts from the leaves of D. viscosa was in the hexane and chloroform crude extracts, and the lowest activity was in the water crude extract, followed by hexane > chloroform > ethyl acetate > methanol > butanol > water crude extracts. One new prenylated flavonoid along with one known compound were isolated from the chloroform crude extract of D. viscosa and were identified by their chemical structures using mass spectrometry, one and two dimension nuclear magnetic resonance. The isolated pure compound also showed significant antioxidant activity against DPPH. This is the first report of antioxidant compounds in the leaves of D. viscosa. The results obtained from this study might be a good natural antioxidant from the selected plant crude extracts.