Hawthorn: Anti-HIV activity of newly identified flavonoids from CrataegusCrataegus species are rich sources of flavonoids and proanthocyanidins, including such compounds as quercetin and rutin. These polyphenolic compounds are responsible for hawthorn’s medicinal benefits. In this study, biologically active constituents of C. sinaica, a plant native to Egypt, were investigated. Researchers isolated three new flavonoids which demonstrated antiviral activity against HIV. A trimeric procyanidin showed the strongest effects. The flavonoids may exert their antiviral effects by binding to the protein coat of the virus itself, or by inhibiting reverse transcriptase in retroviruses like HIV.Shahat A, Ismail S, Hammouda F, et al. Anti-HIV activity of flavonoids and proanthocyanidins from Crataegus sinaicaPhytomedicine 1998; 5(2):133-136.