Seco-labdane diterpenoids from the leaves of Callicarpa nudiflora showing nitric oxide inhibitory activity

Five new seco‐labdane‐type diterpenoids from Caesalpinia latisiliqua

“…The NOESY correlations of H-5 (δ H 2.32) and H-9 (δ H 2.71), H-20 (δ H 0.79), and H b -11 (δ H 3.18)/H a -17 (δ H 4.29)/H a -18 (δ H 4.72) (Figure 3) suggested the configurations of the isopropenyl at C-5, the branch at C-9, and the methyl at C-10 of the six-membered ring as β. Compound 1 showed the negative Cotton effect at 195 and 220 nm, similar to those of 3,4-seco-labdane-type diterpenoids (nudiflopenes A-E), [8] which proved the absolute configurations of chiral carbons in the six-membered ring to be 5S, 9S, and 10S. Thus, the structure of compound 1 was elucidated to be 15-hydroxy-12-oxo-3,4-seco-labda-4(18),8 (17),13(14)E-trien-3-oic acid and named as caesalatisic A.…”

“…The 13 C NMR and HSQC spectra of 1 showed signals of 20 carbons, including two carbonyls at δ C 179.0 (this signal was obtained from HMBC spectrum) and 200.2; six olefinic carbons (including three quaternary, two methylenes, and one methine) at δ C 107.1, 114.0, 137.6, 139.5, 146.9, and 148.4; one quaternary at δ C 40.6; two methines at δ C 44.2 and 50.7; six methylenes at δ C 27.7, 29.7, 32.5, 32.7, 37.0, and 60.1; and three tertiary methyl carbons at δ C 11.8, 18.0, and 23.4. Analysis of the 1 H and 13 C NMR data revealed that 1 was a 3,4-seco-labdane-type diterpenoid and similar to nudiflopene B [8] except for the difference in the chain at C-9. The HMBC correlations from H-17 (δ H 4.29 and 4.74) to C-7 (δ C 37.0)/C-8 (δ C 148.4)/C-9 (δ C 44.2) and from H-19 (δ H 1.75) to C-4 (δ C 146.9)/C-5 (δ C 50.7)/ C-18 (δ C 114.0),and COSY correlations of H-5 (δ H 2.32)/ H-6 (δ H 1.60 and 1.70)/H-7 (δ H 2.13 and 2.34) indicated the isopropenyl group at C-5 and the double bond at C-8/ C-17 (Figure 2).…”

“…The fundamental skeleton of 3,4-secolabdane-type diterpenoid was determined to be similar to that of caesalatisic A by analysis of 1D and 2D NMR spectra and in comparison with Cotton effect in circular dichroism (CD) spectroscopies in the literature. [8] Thus, the structure of compound 2 was defined to be 15-hydroxy-14-oxo-3,4-seco-labda-4(18),8(17),12E-trien-3-oic acid and named as caesalatisic B.…”

seco‐Labdanes: A Study of Terpenoid Structural Diversity Resulting from Biosynthetic C−C Bond Cleavage

“…Six 3,4‐ seco ‐labdanes 38 – 43 were isolated from C. nudiflora in 2018 by Guo and co‐workers [56] . s eco ‐Labdanes 38 – 43 all display the characteristic oxidative A‐ring fission to afford a carboxylic acid (or ester), yet differ in oxidation pattern of carbons 11–16.…”

“…s eco ‐Labdanes 38 – 43 all display the characteristic oxidative A‐ring fission to afford a carboxylic acid (or ester), yet differ in oxidation pattern of carbons 11–16. Of the isolated labdanes, 39 , and 41 – 43 were found to inhibit nitric oxide production in murine microglial BV‐2 cells, with 43 being the most potent (IC 50 =23.3 μ m ) [56] . seco ‐Labdane 44 , a close congener of 38 – 43 , was isolated from the same source by Zhang and co‐workers and also displayed inhibitory activity against nitric oxide production (31.4±4.28 % reduction at 50 μ m ) [57]…”