Anti-HIV-1 protease triterpenoid saponins from the seeds of Aesculus chinensis

Eight bioactive triterpenoid saponins (1−8) were isolated from the seeds of Aesculus chinensis, four of which are novel compounds. The major saponins were identified as escin Ia (1), Ib (2), isoescin Ia (3) and Ib (4), while the new compounds were identified as 22α-tigloyl-28-acetylprotoaescigenin-3β-O-[β-d-glucopyranosyl (1−2)] [β-d-glucopyranosyl (1−4)]-β-d-glucopyranosiduronic acid (escin IVc, 5), 22α-angeloyl-28-acetylprotoaescigenin-3β-O-[β-d-glucopyranosyl (1−2)] [β-d-glucopyranosyl (1−4)]-β-d-glucopyranosiduronic acid (escin IVd, 6), 28-tigloylprotoaescigenin-3β-O-[β-d-glucopyranosyl (1−2)] [β-d-glucopyranosyl (1−4)]-β-d-glucopyranosiduronic acid (escin IVe, 7), and 28-angeloylprotoaescigenin-3β-O-[β-d-glucopyranosyl (1−2)] [β-d-glucopyranosyl (1−4)]-β-d-glucopyranosiduronic acid (escin IVf, 8). The structures were determined by chemical and spectroscopic methods. All the above compounds were evaluated for their inhibitory activity against HIV-1 protease.