Separation of flavonoids with significant biological activity from Acacia mearnsii leaves

Abstract

Acacia mearnsii leaves, which are a rich source of flavonoids, were used to separate and purify myricitrin (W3) and myricetin-3-O-glucoside (W1). Further, the antioxidant and hypoglycemic activities of the two purified flavonoids were evaluated. The flavonoids were separated using solvent partition, macroporous adsorbent resin column, and Sephadex column chromatography, and purified using preparative reverse-phase high-performance liquid chromatography (HPLC). The purified flavonoids were characterized using HPLC, mass spectrometry, and nuclear magnetic resonance methods. A high yield (7.3 mg g^-1 of crude extract) of W3 was obtained, with a high purity of 98.4%. Furthermore, the purity of W1 was over 95%. W1 and W3 showed strong antioxidant activity and significantly inhibited α-glucosidase. W3 also demonstrated substantial α-amylase inhibitory capacity. This study indicated that A. mearnsii leaves, which are discarded in significant amounts, can be used as a source of myricitrin, thus providing more adequate material for the production of antioxidants and type II diabetes inhibitors. Hence, A. mearnsii leaves have the potential to create great market economic value and environmental benefits.

Fig. 1. Chemical structures of flavonoids (A), myricitrin (B), myricetin-3-O-glucoside (C), and myricetin-3-O-arabinoside (D).

Fig. 2. HPLC chromatographic spectra of BFr3 fraction and isolated flavonoids: W1, W2, and W3.

Fig. 3. HPLC spectra of W1 (myricetin-3-O-glucoside) (A), W2 (myricetin-3-O-arabinoside) (B), and W3 (myricitrin) (C).

Fig. 4. Scavenging activity of W1, W2 and W3 on (A) DPPH radical, (B) ABTS radical, and their (C) FRAP value.

Fig. 5. Effect of W1, W2 and W3 of (A) α-glucosidase and (B) α-amylase activity.