Flavonoids from Biophytum petersianum, a Malian medicinal plant

We have previously reported that the tropical herb Biophytum petersianum Klotzsch. is used in

Mali against cerebral malaria, pain, and as a wound healing agent.

6-[6-Deoxy-α-L-mannopyranosyl)-β-L-ribo-hexopyranos-3-ulos-1-yl]-apigenin (cassiaoccidentalin A) was isolated from the plant. This is a very rare flavonoid, having been reported once before in nature. A second flavonoid has been assigned the structure apigenin 6-(2-propenoic acid). This is a new natural product. Protocatechuic acid (3,4-dihydroxybenzoic acid) was also isolated and identified. This is a fairly common compound in nature.

The methanolic extract of the plant was a good inhibitor of xanthine oxidase (IC₅₀ 26±6µg/ml),

an enzyme that is important for peroxidative processes by catalyzing the formation of superoxide radical anion. Most of the inhibitory activity was found in the ethyl acetate fraction. The crude extract was only moderately active as a scavenger of the DPPH radical or as inhibitor of 15-lipoxygenase. Protocatechuic acid was inactive as XO scavenger and 15-LO inhibitor, but scavenged DPPH radical (IC₅₀ 71±13µM); cassiaoccidentalin A was a poor radical scavenger and showed moderate activity as XO inhibitor (IC₅₀ 75±6µM) and 15-LO inhibitor (IC₅₀ 112±9µM). It appears that other, so far unidentified XO inhibitors are present in the ethyl acetate extract. Apigenin 6-(2-propenoic acid) was not present in sufficient amount for activity assays.