Anti-HIV-1 protease activity of compounds from Boesenbergia pandurata

Searching for anti-HIV-1 protease (PR) inhibitors of Thai medicinal plants led to the isolation of a new cyclohexenyl chalcone named panduratin C ( 1) and chalcone derivatives ( 2– 6) from the methanol extract of Boesenbergia pandurata rhizomes. The known compounds were identified to be panduratin A ( 2), hydroxypanduratin A ( 3), helichrysetin ( 4), 2′,4′,6′-trihydroxyhydrochalcone ( 5), and uvangoletin ( 6). It was found that 3 possessed the most potent anti-HIV-1 PR activity with an IC 50 value of 5.6 μM, followed by 2 (IC 50 = 18.7 μM), whereas others exhibited mild activity. Structure–activity relationships of these compounds on anti-HIV-1 PR activity are summarized as follows: (1) hydroxyl moiety at position 4 conferred higher activity than methoxyl group; (2) prenylation of dihydrochalcone was essential for activity; (3) hydroxylation at position 4‴ reduced activity; and (4) introduction of double bond at C1′ and C6′ of chalcone gave higher activity. Searching for anti-HIV-1 protease (PR) inhibitors of Thai medicinal plants led to the isolation of a new cyclohexenyl chalcone named panduratin C ( 1) and chalcone derivatives ( 2– 6) from the methanol extract of Boesenbergia pandurata rhizomes. The known compounds were identified to be panduratin A ( 2), hydroxypanduratin A ( 3), helichrysetin ( 4), 2′,4′,6′-trihydroxyhydrochalcone ( 5), and uvangoletin ( 6). The structures of all compounds were elucidated on the basis of chemical and spectroscopic methods. It was found that 3 possessed the most potent anti-HIV-1 PR activity with an IC 50 value of 5.6 μM, followed by 2 (IC 50 = 18.7 μM), whereas other compounds exhibited only mild activity. Structure–activity relationships of these compounds on anti-HIV-1 PR activity are summarized as follows: (1) hydroxyl moiety at position 4 conferred higher activity than methoxyl group; (2) prenylation of dihydrochalcone was essential for activity; (3) hydroxylation at position 4‴ reduced activity; and (4) introduction of double bond at C1′ and C6′ of chalcone gave higher activity. As regards active constituents contained in B. pandurata rhizomes, hydroxypanduratin A ( 3) and panduratin A ( 2) are active principles against HIV-1 PR.