Flavonoid composition, antibacterial and antioxidant properties of tartary buckwheat bran extract

The tartary buckwheat [Fagopyrum tataricum (L.) Gaench] bran, which is an important by-product during the production of tartary buckwheat tea, is a good source of flavonoids but has not been made full use of. Some studies reveal its antioxidant activity. However no research is found for its antibacterial activities against Propionibacterium and Staphylococci species. The 60% (v/v) EtOH extract of the tartary buckwheat bran (TBBE) was prepared at room temperature and the flavonoids content was determined by HPLC. Rutin (541.3 ± 9.3 mg/g), isoquercetin (9.33 ± 0.16 mg/g) and quercetin (66.3 ± 1.14 mg/g) were detected in the TBBE. The inhibition zone of TBBE against four bacterial strains varied from 7.6 mm to 11.6 mm; minimum inhibition concentration (MIC) values were from 512 μg/mL to 2048 μg/mL. IC50 of DPPH scavenging activity and relative ORAC values were 8.36 ± 0.27 μg/mL and 11,090 ± 1278 μmol TE/g, respectively. For the constituents of TBBE querectin showed higher antioxidant and antibacterial properties than TBBE and its glycosides (isoquercetin and rutin). These results suggest that TBBE might be useful to develop new types of antibacterial substance and new skin care cosmetics to prevent or improve acne.