Bioassay-guided isolation of neo-clerodane diterpenoids fromScutellaria barbata

Abstract

Bioassay-guided isolation of the aerial part of Scutellaria barbata yielded three new neo-clerodane diterpenoids scutebatas P-R (1-3), together with two known ones: scutebata E (4) and scutebarbatine B (5). The chemical structures of the isolated compounds were elucidated by spectroscopic methods (NMR and MS) and by comparison with the spectroscopic data reported in the literature. All compounds except 3 showed weak cytotoxicity with IC50 values ranging from 35.11 to 42.73 μM against K562 cell lines, and compounds 1, 2, and 5 also displayed weak activities against HL60 cell lines.

Cytotoxic Neo‐Clerodane Diterpenoids from Scutellaria barbata D.Don

“…[16] These data suggested the necessity of a substitution at the C(11) position for the cytotoxic activity against LoVo and HCT-116 cells. Compounds 13-16 possessed the similar structure except for the substituted groups at C(6) and C (7). Both, 14 and 16, possessed a benzoyloxy group at C (7) and showed significant cytotoxic activity toward four tested tumor cells, furthermore, the former also had a benzoyloxy group at C(6), while the latter was substituted by a nicotinoyloxy group, exhibited stronger cytotoxic activities.…”

“…Compounds 13-16 possessed the similar structure except for the substituted groups at C(6) and C (7). Both, 14 and 16, possessed a benzoyloxy group at C (7) and showed significant cytotoxic activity toward four tested tumor cells, furthermore, the former also had a benzoyloxy group at C(6), while the latter was substituted by a nicotinoyloxy group, exhibited stronger cytotoxic activities. Comparing 13 with 15, compound 13 substituted by hydroxy at C(7) displayed the less effect on cytotoxic activity against LoVo and HCT-116 cells than 15 substituted by a nicotinoyloxy group.…”

“…Biodiversity 2019, 16, e1800499 www.cb.wiley.com (2 of 6) e1800499 © 2019 Wiley-VHCA AG, Zurich, Switzerland C(1') indicated that the acetyl group was attached to C (6). Moreover, the cross-peaks from HÀ C(1) (δ(H) 5.83) to C(3) and C(1'''), HÀ C(7) (δ(H) 5.53) to C(6) and C(1'') revealed that the two nicotinoyloxy groups were attached to C(1) and C (7), respectively. Based on all of the data the structure of compound 1 was established as shown in Figure 1 and compound 1 named as barbatin H. Other fifteen known diverse neo-clerodane diterpenoids, named scutebata P (2), [7] scutebarbatine F (3), [8] 6-O-nicotinoylscutebarbatine G (4), [9] scutebata G (5), scutebata E (6), scutebata D (7), [10] barbatin C (8), [3] scutebarbatine A (9), [11] scutebarbatine G (10), [12] scutebarbatine B (11), [3] 6,7-di-O-acetoxybarbatin A (12), [13] scutebata C (13), scutebata A (14), [10] scutebarbatine X (15), [14] and scutebata B (16) [15] were isolated from the stem of S. barbata by silica gel column, RPÀ C18 CC, Sephadex LH-20, and preparative HPLC, characterized by NMR and HR-MS data and compared with those reported in the literature.…”

“…Other fifteen known diverse neo-clerodane diterpenoids, named scutebata P (2), [7] scutebarbatine F (3), [8] 6-O-nicotinoylscutebarbatine G (4), [9] scutebata G (5), scutebata E (6), scutebata D (7), [10] barbatin C (8), [3] scutebarbatine A (9), [11] scutebarbatine G (10), [12] scutebarbatine B (11), [3] 6,7-di-O-acetoxybarbatin A (12), [13] scutebata C (13), scutebata A (14), [10] scutebarbatine X (15), [14] and scutebata B (16) [15] were isolated from the stem of S. barbata by silica gel column, RPÀ C18 CC, Sephadex LH-20, and preparative HPLC, characterized by NMR and HR-MS data and compared with those reported in the literature.…”

“…Compound 2, 14, and 16 exerted the strong cytotoxic activity toward LoVo and HCT-116 cells. All of them were substituted at C(11) by ester moieties, and possessed at least one benzoyloxy group at C(11), C(6), or C (7). Moreover 14 possessed two benzoyloxy groups at C(6) and C (7), respectively, and showed the Chem.…”