An unprecedented antioxidative isopimarane norditerpenoid from bivalve clam, Paphia malabarica with anti-cyclooxygenase and lipoxygenase potential

Figures & data

Table 1. NMR spectroscopic data in CDCl₃.

1
C. No.	^13C	^1H (int., mult., J in Hz)^a	^1H-^1H COSY	HMBC
1	129.71	5.37 (1H, dd overlap, 7.24)	H-10	C-11
2	130.01	5.38 (1H, dd overlap, 8.51)	H-3	C-4, 21
3	71.83	3.53 (1H^α, td)	H-4	–
4	42.24	2.29 (2H, d)	–	C-5, 6, 3
5	140.72	–	–	–
6	121.72	5.34 (1H, t, 6.61)	H-7	–
7	39.52	2.01 (2H, d)	–	C-6
8	42.32	–	–	–
9	50.14	0.91 (1H, m)	H-11	C-13, 14
10	28.23	2.81 (1H, dd)	–	C-14
11	31.93	1.49 (1H^β, m), 1.85 (1H^α, m)	H-12	–
12	37.25	1.83 (1H, t), 1.08 (1H, t)	–	–
13	36.50	–	–	–
14	56.77	1.12 (1H^β, m)	H-18	–
15	22.69	1.15 (2H, d)	H-16	C-18, 19
16	14.11	0.89 (3H, t)	–	C-18, 19
17	11.86	0.68 (3H^α, s)	–	C-12, 14, 8
18	22.82	0.86 (3H, d)	–	C-19, 11, 8
19	19.39	1.01 (3H^α, s)	–	C-16, 13, 9, 5
20	68.35	3.64 (2H, t)	H-21	C-3
21	29.70	1.61 (2H, m)	H-22	–
22	65.03	4.15 (2H, t)	–	–
23	178.23	–	–	–
24	33.87	2.33 (2H, t)	H-25	C-25, 23
25	24.75	1.63(2H, m)	H-26	C-24, 23
26	21.09	1.44 (2H, m)	H-27	C-24, 25
27	18.72	0.87 (3H, t)	–	–

¹H NMR spectra recorded using Bruker AVANCE III 500 MHz (AV 500) spectrometer (Bruker, Karlsruhe, Germany) in CDCl₃ as aprotic solvent at ambient temperature with TMS as the internal standard (δ 0 ppm).

The ¹H NMR spectra were recorded at 500 MHz, while the ¹³C NMR spectra were recorded at 125 MHz.

^a Values in ppm, multiplicity and coupling constants (J = Hz) are indicated in parentheses.

The assignments were made with the aid of the ¹H-¹H COSY, HSQC, HMBC and NOESY experiments.

Figure 1. Key (A) ¹H − ¹H COSY, (B) HMBC and (C) NOESY correlations of 18 (4 → 14), 19 (4 → 8)-bis-abeo nor-isopimarane-1, 5-diene-3-yl-3β-methoxy propyl pentanoate.

Table 2. Antioxidant and anti-inflammatory activities of the title compound from P. malabarica and the commercially available antioxidants and anti-inflammatory agents (α-tocopherol and ibuprofen).

	IC50 (mg/mL)
Antioxidant activities	Isopimarane norditerpenoid	α-Tocopherol
^cDPPH scavenging	0.65 ± 0.02^a	0.63 ± 0.04^a
^cABTS^+ scavenging	0.78 ± 0.06^a	0.73 ± 0.05^a
Anti-inflammatory activities	Isopimarane norditerpenoid	Ibuprofen
^cCOX-1 inhibition	0.70 ± 0.02^a	0.04 ± 0.00^b
^cCOX-2 inhibition	0.82 ± 0.05^a	0.09 ± 0.02^b
^dSelectivity index	0.85 ± 0.04^a	0.44 ± 0.03^b
^c5-LOX inhibition	0.75 ± 0.06^a	0.93 ± 0.11^b

^c The bioactivities were expressed as IC₅₀ values (mg/mL).

The samples were analyzed in triplicate (n = 3) and expressed as mean ± standard deviation. Means followed by the superscript letters (a and b) within the same row indicate significant differences (p < 0.05).

^d Selectivity index has been calculated as the ratio of anti-COX-1(IC₅₀) and anti-COX-2 (IC₅₀).