LAUSR

The club moss Palhinhaea cernua (Lycopodium cernuum) of the family Lycopodiaceae is a perennial herb mainly distributed in Eastern and Southern China, the dried whole plant of which is historically used as a traditional Chinese medicine (TCM) for the treatment of rheumatism, whooping cough, contusions, scalds, hepatitis, and nephrolithiasis [1, 2]. Previously, an array of structurally interesting secondary metabolites, mainly serratane-type triterpenoids and Lycopodium alkaloids, were isolated from this plant [3, 4]. These isolated constituents have attracted a great deal of interest due of their wide range of biological activities, such as the inhibitory activities against cholinesterases and β-secretase 1, which were regarded as the key targets for the treatment of Alzheimer′s disease (AD) [3, 5]. As part of our research on structurally unique and biologically active metabolites from the Chinese medicinal plants [6], we investigated the title plant. The dried and powdered whole plant of P. cernua was extracted with MeOH to get a dark brown extract, which was subjected to a series of chromatographic techniques to yield 21 compounds. These isolates were identified as α-onocerin (1) [7], α-onocerin diacetate (2) [8], α-onoceradienedione (3) [9], serratenediol (4) [10], seratenediol-3-acetate (5) [11], seratenediol3,21-diacetate (6) [11], 21-episerratenediol (7) [10], 21-episerratenediol-3-acetate (8) [11], 21-episerratenediol-3,21-diacetate (9) [12], serratenedione (10) [13], serratriol (11) [14], serratriol triacetate (12) [15], 21-episerratriol (13) [14], 21-episerratriol triacetate (14) [16], lycoclavanol (15) [10], lycoclavanol triacetate (16) [15], 16-oxo-21-episerratriol (17) [17], 16-oxo-21episerratriol triacetate (18) [17], 16-oxolycoclavanol (19) [18], 16-oxolycoclavanol triacetate (20) [17], and lycernuic acid A (21) [18]. Their structures were established by means of spectroscopic methods as well as comparison with literature data, including NMR, which agreed perfectly with the published data. α-Onocerin (1), white amorphous powder. C30H50O2. 1H NMR (300 MHz, C5D5N, δ, ppm, J/Hz): 0.78 (6H, s, H-25, 28), 1.04 (6H, s, H-24, 30), 1.24 (6H, s, H-23, 29), 3.52 (2H, dd, J = 10.1, 5.5, H-3, 21), 4.81 (2H, s, H-26, 27), 5.04 (2H, s, H-26, 27), 5.84 (2H, br.s, 3, 21-OH). 13C NMR (100 MHz, C5D5N, δ, ppm): 37.5 (C-1, 19), 28.9 (C-2, 20), 77.9 (C-3, 21), 39.7 (C-4, 22), 55.0 (C-5, 17), 24.5 (C-6, 16), 38.7 (C-7, 15), 149.3 (C-8, 14), 57.9 (C-9, 13), 39.7 (C-10, 18), 23.1 (C-11, 12), 28.9 (C-23, 29), 16.3 (C-24, 30), 14.9 (C-25, 28), 106.9 (C-26, 27) [7]. α-Onocerin diacetate (2), white amorphous powder. C34H54O4. 1H NMR (300 MHz, CDCl3, δ, ppm, J/Hz): 0.66 (6H, s, H-25, 28), 0.83 (6H, s, H-24, 30), 0.89 (6H, s, H-23, 29), 2.05 (6H, s, COCH3), 4.52 (2H, dd, J = 11.9, 4.2, H-3, 21), 4.55 (2H, br.s, H-26, 27), 4.83 (2H, br.s, H-26, 27) [8]. α-Onoceradienedione (3), white amorphous powder. C30H46O2. 1H NMR (300 MHz, CDCl3, δ, ppm): 0.81 (6H, s, H-25, 28), 1.00 (6H, s, H-24, 30), 1.08 (6H, s, H-23, 29), 4.60 (2H, br.s, H-26, 27), 4.89 (2H, br.s, H-26, 27) [9]. Serratenediol (4), white amorphous powder. C30H50O2. 1H NMR (300 MHz, C5D5N, δ, ppm, J/Hz): 0.81 (3H, s, H-28), 0.90 (3H, s, H-25), 0.97 (3H, s, H-26), 1.09 (3H, s, H-24), 1.13 (3H, s, H-29), 1.22 (3H, s, H-30), 1.27 (3H, s, H-23), 3.49 (1H, dd, J = 15.3, 6.0, H-3), 3.54 (1H, dd, J = 15.3, 6.0, H-21), 5.50 (1H, br.s, H-15), 5.82 (1H, br.s, OH), 5.92 (1H, br.s, OH). 13C NMR (100 MHz, C5D5N, δ, ppm): 39.0 (C-1), 28.5 (C-2), 77.9 (C-3), 39.6 (C-4), 56.0 (C-5), 19.4 (C-6), 45.5 (C-7), 37.4 (C-8), 62.9 (C-9), 38.4 (C-10), 25.5 (C-11), 27.5 (C-12), 57.6 (C-13), 138.7 (C-14), 122.7 (C-15), 24.6 (C-16), 50.0