Eleven compounds were isolated from the methanol extract of the leaves of Solanum erianthum D. Don, including five α-linolenic acid analogs, α-linolenic acid (1), 13 S-hydroxy-9(Z),11(E)-octadecadienoic acid (2), 9S-hydroxy-10(E),12(Z), 15(Z)-octadectrienoic acid (3), 9(Z),11(E)-octadecadienoic acid (4), and octadecanoic acid (5); two benzofuran-type lactones, loliolide (6) and dihydroactinidiolide (7); two steroidal alkaloids, solasonine (8) and solamargine (9); a flavonol glycoside, camelliaside C (10); and a flavone, 5-methoxy-(3″,4″-dihydro-3″,4″-diacetoxy)-2″,2″-dimethylpyrano-(7,8:5″,6″)-flavone (11). Among these isolated compounds, 9 showed the most potent activity against HBsAg, with an IC50 of 1.57 μM, followed by 8(IC50 is 5.89 μM). In the testing against HBeAg, 11 was the only active compound with an IC50 of 36.11 μM. Compound 9 also revealed strong inhibition of DNA replication towards HBV and its IC50 was 2.17 μM. However, α-linolenic acid (1) showed a prominent selected index (SI), both in anti-HBsAg and inhibition of DNA replication with SI values of 7.75 and 7.18, respectively. This is the first report that unsaturated fatty acid 1, steroidal alkaloid glycoside 9 and flavone 11, all showed excellent activity against HBV. These results provide lead candidates in the development of anti-HBV drugs from natural sources.
KimTG, KangSY, JungKK, KangJH, LeeE, HanHM, KimSH. (2001) Antiviral activities of extracts isolated from Terminalis chebula Retz., Sanguisorba officinalis L., Rubus coreanus Miq. and Rheum palmatum L. against hepatitis B virus. Phytotherapy Research, 15, 718–720
2.
HuangTC. (1998) Flora of Taiwan, Department of Botany, National Taiwan University, 2nd Ed., Vol 4, Taipei, Taiwan, 566–567.
3.
ChiuNY, ChangKH. (1992) The Illustrated Medicinal Plants of Taiwan, SMC Publishing Inc, 2nd Ed., Vol 1, Taipei, Taiwan, 191.
4.
PesewuGA, CutlerRR, HumberDP. (2008) Antibacterial activity of plants used in traditional medicines of Ghana with particular reference to MRSA. Journal of Ethnopharmacology, 116, 102–111.
YamashitaT, FujimuraN, YaharaS, NoharaT, KawanobuS, FujiedaK. (1990) Structures of three new steroidal alkaloid glycol-sides, solaverines I, II, III from Solanum toxicarium and S. verbascifolium. Chemical and Pharmaceutical Bulletin, 38, 827–829.
7.
ZhouLX, DingY. (2002) A cinnamide derivative from Solanum verbascifolium L. Journal of Asian Natural Products Research, 4, 185–187.
8.
OhtsukiT, MiyagawaT, KoyanoT, KowithayakornT, IshibashiM. (2010) Isolation and structure elucidation of flavonoid glycosides from Solanum verbascifolium. Phytochemistry Letters, 3, 88–92.
9.
KimuraJ, NoritsuguM. (2002) New loliolide derivatives from the brown alga Undaria pinnatifida. Journal of Natural Products, 65, 57–58.
10.
SakanT, IsoeS, HyeonSB. (1967) The structure of actinidiolide, dihydroactinidiolide and actinidol. Tetrahedron Letters, 8, 1623–1627.
11.
RouessacF, ZamarlikH, GnonlonfounN. (1983) Synthese du (±) loliolide par polycyclisation de l'acide homogeranique. Tetrahedron Letters, 24, 2247–2250.
12.
FukuharaK, KuboI. (1991) Isolation of steroidal glycoalkaloids from Solanum incanum by two countercurrent chromatographic methods. Phytochemistry, 30, 685–687.
13.
SekineT, AraiY, IkegamiF, FujiiY, ShindoS, YanagisawaT, IshidaY, OkonogiS, MurakoshiI. (1993) Isolation of camelliaside C from “tea seed cake” and inhibitory effects of its derivatives on arachidonate 5-lipoxygenase. Chemical and Pharmaceutical Bulletin, 41, 1185–1187.
14.
Carcache-BlancoEJ, KangYH, ParkEJ, SuBN, KardonoLB, RiswanS, FongHH, PezzutoJM, KinghornAD. (2003) Constituents of the stem bark of Pongamia pinnata with the potential to induce quinone reductase. Journal of Natural Products, 66, 1197–1202.
15.
GuoG, ZhaoL, YouQ, YangY, GuH, SongG, LuN, XinJ. (2010) Anti-hepatitis B virus activity of wogonin in vitro and in vivo. Antiviral Research, 74, 16–24.
16.
LeuG-Z, LinT-Y, HsuJ. (2004) Anti-HCV activities of selective polyunsaturated fatty acids. Biochemical and Biophysical Research Communications, 318, 275–280.
