Free radical scavengers from the barks of Carallia brachiata Merr

In a search for bioactive compounds, the crude extracts from the barks of Carallia brachiata Merr. showed significant free radical scavenging activity. This plant was selected for further study on chemical constituents. The fractionation of dichloromethane and ethyl acetate crude extracts led to the isolation of one new compound, afzelechin-(4→6, 2→O→7)- afzelechin-(4→8, 2→O→7)- afzelechin together with three known mixtures and two pure compounds, a mixture of long chain aliphatic esters, a mixture of a stigmasterol and β-sitosterol, a mixture of alkyl trans-ferulate ester, p-hydroxybenzoic acid and afzelechin-(4→8, 2→O→7)-epiafzelechin. The new compound was elucidated by spectroscopic method. The biological activities results indicated that a mixture of alkyl trans-ferulate ester, afzelechin -(4→8, 2→O→7)-epiafzelechin and afzelechin-(4→8, 2→O→7)-afzelechin-(4→8, 2→O→7)-afzelechin showed significant activity on DPPH with IC₅₀ 134.96, 98.86, 83.49 µg/ml, respectively. Afzelechin-(4→8, 2→O→7)-epiafzelechin and afzelechin-(4→6, 2→O→7)-afzelechin-(4→8, 2→O→7)-afzelechin also showed antioxidant activity with ferric thiocyanate assay. In addition, afzelechin-(4→8, 2→O→7)- epiafzelechin and afzelechin-(4→6, 2→O→7)- afzelechin -(4→8, 2→0→7)- afzelechin were exhibited strong activities on superoxide dismutase and xanthine oxidase inhibition methods by comparison with BHA and allopurinol, respectively.