Modified ent-Abietane Diterpenoids from the Leaves of Suregada zanzibariensis

Abstract

The leaf extract of Suregada zanzibariensis gave two new modified ent -abietane diterpenoids, zanzibariolides A ( 1 ) and B ( 2 ), and two known triterpenoids, simiarenol ( 3 ) and β-amyrin ( 4 ). The structures of the isolated compounds were elucidated based on NMR and MS data analysis. Single-crystal X-ray diffraction was used to establish the absolute configurations of compounds 1 and 2 . The crude leaf extract inhibited the infectivity of herpes simplex virus 2 (HSV-2, IC 50 11.5 μg/mL) and showed toxicity on African green monkey kidney (GMK AH1) cells at CC 50 52 μg/mL. The isolated compounds 1 – 3 showed no anti-HSV-2 activity and exhibited insignificant toxicity against GMK AH1 cells at ≥100 μM.

Ethnomedicinal Uses, Phytochemistry and Pharmacological Properties of Suregada Genus: A Review

“…Kalenga reported that modified ent-abietane diterpenoids with a terminal olefinic bond at C-4, such as in compounds 58 and 59, are rare. The terminal double bond at C-4 is proposed to arise through an enzymatic 1,2-methyl shift, either of CH 3 -18 or CH 3 -19, from C-4 to C-3, followed by dehydrogenation [46]. The suggested biosynthesis for compounds 58 and 59 is shown in Scheme 2 [46].…”

“…The terminal double bond at C-4 is proposed to arise through an enzymatic 1,2-methyl shift, either of CH 3 -18 or CH 3 -19, from C-4 to C-3, followed by dehydrogenation [46]. The suggested biosynthesis for compounds 58 and 59 is shown in Scheme 2 [46]. The oxidation of ent-copalyl PP leads to the production of ent-pimaradiene.…”

“…Then, the ent-pimaradiene could be oxidized to obtain an intermediate containing a lactone ring which is an ent-abietane diterpenoid skeleton. The ent-abietane diterpenoid skeleton may undergo a series of transformations namely, hydrogenation, and dehydrogenation, and then followed by enzymatic 1.2 methyl shift to produce compound 58 or epoxidation for compound 59 [46]. The 1 H NMR spectrum of compound 4 (Figure 1) showed the presence of a trisubstituted cyclopropane ring.…”

“…Ent-abiatene diterpenoids 7β,8αβ-dihydroxy-12-oxo-ent-abietan-16,14-olide (36), 3,4,18βcyclopropa-7β,17-dihydroxy-ent-abieta-8(14),13(15)-dien-16,12-olide (37), 3α,7β-dihydroxyent-abieta-8(14),13(15)-dien-16,12-olide (38), 7β-hydroxy-ent-abieta-8(14),13(15)-dien-16,12olide (39), 3-oxo-8β,14β-epoxy-ent-abieta-11,13(15)-dien-16,12-olide (40), 13α-Hydroxy-14α,16-epoxy-ent-abieta-7-en-3-one (41), 7-Oxo-ent-abieta-5,8 (14),13(15)-trien-16,12-olide (42), Methyl 12-hydroxy-3-oxo-ent-abieta-8,11,13-trien-17-oate (43), 3-oxo-jolkinolide B (44), 3,4,18b-cyclopropa-ent-abieta-8 (14),13(15)-dien-16,12-olide (45) and 7β,17-dihydroxyent-abieta-8 (14),13(15)-dien-16,12-olide (46) were isolated from the ethanol extract of S. glomerulata roots (Blume) Baill. [51][52][53].…”

“…Investigation of methanol-dichloromethane (1:1) extract of S. multiflora leaves afforded ten diterpene lactones namely, 3β,6β-diacetoxy-1one-8β,14β-epoxy-13,15-abiatene-16,12-olide (48), 3β-hydroxy-1-one-8β,14β-epoxy-13,15abiatene-16,12-olide (49), 3β-acetoxy-8β,14α-dihydroxy-13,15-abiatene-16,12-olide (50), 6βacetoxy-2-ene-8β,14α-dihydroxy-1-one-13,15-abiatene-16,12-olide (51), 3β-acetoxy-8β,14αdihydroxy-1-one-13,15-abiatene-16,12-olide (52), 3β-acetoxy-8β,14β-epoxy-13,15-abiatene-16,12-olide (53), 3β,6b-diacetoxy-8β,14β-epoxy-13,15-abiatene-16,12-olide (54), 3β-acetoxy-1-one-8β,14β-epoxy-13,15-abiatene-16,12-olide (55), 2-ene-1-one-8β,14β-epoxy-13,15-abiatene-16,12-olide (56), and 6β-acetoxy-2-ene-1-one-8β,14β-epoxy-13,15-abiatene-16,12-olide (57) [15]. S. zanzibariensis leaf extract yielded zanzibariolides A (58) and B (59) [46]. 66), euphoranginol B (67), corymbol (68), and ent-kaurane-3β,16β,17-triol (69) (Figure 4) [52,53].…”