Identification of 16β,17-dihydroxy-(-)-kauran-19-oic acid as an anti-HIV principle and isolation of related new kaurane diterpenoids from Annona squamosa - Wu,Y.C.; Hung,Y.C.; Chang,F.R.; Cosentino,M.; Wang,H.K.; Lee,K.H. (J Nat Prod, 1996)