Eleven compounds were isolated from the methanolic extract of the leaves of Solanum erianthum D. Don, including five -linolenic acid analogs, -linolenic acid (1), 13S-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 IC 50 of 1.57 M, followed by 8 (IC 50 is 5.89 M). In the testing against HBeAg, 11 was the only active compound with an IC 50 of 36.11 M. Compound 9 also revealed strong inhibition of DNA replication towards HBV and its IC 50 was 2.17 M. However, -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.