Isolation of flavonoids and a chalcone from Helichrysum odoratissimum and synthesis of helichrysetin.

3,5-Dihydroxy-6,7,8-trimethoxyflavone, 3-O-methylquercetin, and helichrysetin were isolated from the flowers of the Rwandese medicinal plant, Helichrysum odoratissimum. Because of inconsistencies of the mp of the latter chalcone, a synthesis of helichrysetin was developed. 3-O-Methylquercetin was shown to be an active principle as it displayed antimicrobial activity.