Radical scavenging activities of Kaempferia larsenii Sirirugsa extract and prominent flavonoids in its rhizomes

Abstract

Medicinal plants of the genus Kaempferia (Zingiberaceae) have long been valued in Thailand, where their fresh rhizomes, extracts and oils are utilized for traditional medicinal purposes. While the well-known Kaempferia plants, particularly K. galanga and K. parviflora have been scientifically proven to be effective medicinal herbs in antioxidative investigations and in a variety of pharmacological activities, K. larsenii, one of the members of this genus that is found in northeastern Thailand and has long been used by local practitioners for curative purposes, has never had the chemical constituents and antioxidant activity reported before. Thus, the purpose of this study was to determine the antioxidant capacity of the plant and the active chemical components accountable for its action. K. larsenii rhizome extract was subjected to a number of antioxidative tests, including 2,2?-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid), 2,2-diphenyl-1-picrylhydrazyl, superoxide anion and hydroxyl radical scavenging activities, as well as HPLC analyses. The HPLC method used a ZORBAX Eclipse Plus C18 column, a 1 mL/min flow rate of methanol and 0.1% (v/v) phosphoric acid (55:45) and a diode-array UV absorbance at 265 nm as the stationary phase, mobile phase and detection respectively. In the investigated assays, the plant extract exhibited remarkable antioxidant activity, with EC50 values ranging from 11.60 to 26.31 µg/mL. Its efficacy was significantly higher than that of the positive controls, which had EC50 values ranging from 13.08 to 29.91 µg/mL. According to the HPLC profile of the extract, the medicinal flavonoids kaempferol and quercetin were present in the sample at % of 12.7562 and 0.4976 (w/w) respectively. K. larsenii rhizome extract is a good source of antioxidants and has the potential to be incorporated into herbal medicinal preparations that would be beneficial for health.