| 摘要: | 從天然物中尋找新藥逐漸受到重視，茄科植物乃世界上第三大經濟作物，且多含有良好的生物活性，其中之一的印度茄，在台灣更是常被作為草藥，主要成份為固醇類皂苷（steroidal glycosides）和固醇類生物鹼（steroidal alkaloid），茄科在過去的研究中發現在環境中具有自毒作用的現象，固醇類生物鹼亦被證明會對其它植物產生毒性，因此本研究希望以印度茄葉粉水溶萃取液經過長時間分解及莖部甲醇萃取為方向，分別對於植物相生相剋及抗肝癌活性進行探討。
在印度茄葉粉水溶萃取液的方面測試了小白菜、萵苣、九層塔、小米、大花咸豐草等種子進行了植物相生相剋之活性測試，發現即便經過第四週的分解，對於上述五種種子之幼根生長抑制率及發芽率，仍有顯著的效果，表示印度茄葉粉水溶萃取液，不論是否有經過分解處理，對測試植物之幼根生長及發芽，皆有抑制效果，其中以無分解及第一次萃取最高，後面效果漸漸減低。對水溶萃取液進行紙色層分析發現含有酚酸物質與類黃酮，如 caffeic acid、chlorogenic acid、 trimethoxybenzoic acid，並利用 XAD-2 樹脂，Sephadex LH-20 與逆相高效液相層析分離得到 3,5,6,9-tetrahydroxy-7-megastigmene，此化合物過去亦證實會抑制植物幼根生長。可見在印度茄中除了過去所提出的固醇類生物鹼，仍有許多物質會產生相生相剋的作用。
在細胞活性的測試部分，以印度茄莖部進行甲醇萃取後以乙酸乙酯與水進行液－液分配，得到乙酸乙酯層，再將此乙酸乙酯層進行分離，得到了 13 個分離層（SVS-1~SVS-13），將這 13 個分離層對於肝癌細胞 HepG2 2.2.15 進行細胞毒殺實驗，發現 SVS-5~SVS-8 這四個分離層在低於給予藥物濃度 40 μg/ml 情況，具有良好的細胞活性，遂著手進行分離及純化之步驟，並從中得到 rutin、β-sitosterol/stigmasterol、palmitic acid、lignoceric acid，而以純物質進行細胞毒殺測試觀察到 lignoceric acid 在 20 μg/ml 即能夠產生 50 % 的細胞毒殺活性，代表印度茄確實有很大的藥理潛力。
綜合上面所述，印度茄具有良好的藥理活性，且含有相生相剋物質，但皆與過去文獻所提到得不同，可見印度茄上具有相當大的潛能值得去開發其藥用資源，並探究植物相生相剋作用機轉。
Natural product has been received increasingly as an alternative source for the treatment of human diseases. The solanaceous plants, which possess biological activity, are the third important economic crops on the earth. One of these, Solanum violaceum Ortega was used as folk medicine in Taiwan. Steroidal glycosides and steroidal alkaloids are active ingredients of S. violaceum. According to the literature, the solanaceous plants also show autotoxicity in the environment. Steroidal alkaloids are identified as toxic compounds to other plants in the review papers. In this study, we used the aqueous, methanolic extract of leaves to test the allelopathy and cytotoxicity, respectively.
In order to test the allelopathic potential of S. violaceum, the aqueous extracts of leaves of S. violaceum were bioassayed against 5 tested plants, namely, Brassica chinensis, Lactuca sativa, Setaria italica, Ocimum basilicum and Bidens pilosa using standard sponge bioassay (SSB). The decomposition experiment was conducted to understand its potency of phytotoxicity. The result revealed that the phytotoxicity remained active to the inhibition of radicle length in a four-week decomposition experiment. We also found the most inhibitory effect was shown in the non-decomposition and first aqueous leaves extract, the phytotoxicity decreased in the subsequent extracts. Furthermore, phytotoxic phenolics, such as caffeic acid, chlorogenic acid and trimethoxybenzoic acid were tentatively identified as comparison with authentic compounds by means of paper chromatography. The aqueous extract of leaves was separated into 5 factions. The 3,5,6,9-tetrahydroxy-7-megastigmene was isolated from the second fraction. This compound also identified as an allelochemical which inhibited the radicle length. Therefore, besides the steroidal alkaloids, there are more allelochemicals needed to be found in S. violaceum.
On the other hand, the methanolic extract from stem of S. violaceum possessed cytotoxic effects. Therefore, the extract was liquid-liquid partitioned by using ethyl acetate (EtOAc) and water. The EtOAc layer was separated into 13 fractions in a gradient eluted by n-hexanes and EtOAc ( SVS-1~SVS-13 ). The active fractions were found between fractions 5 to 8 at concentration below 40 μg/ml in the cytotoxic testing of HepG2 2.2.15. These results clearly suggested that the partially purified fractions of S. violaceum had the phytotoxic potential to germination, radicle length and cytotoxicity. Five compounds isolated from methanolic stem extract of S. violaceum are rutin, a mixture of β-sitosterol/stigmasterol, palmitic acid, lignoceric acid. Lignoceric acid reveal 50 % inhibitory activity at 20 μg/ml on HepG2 2.2.15. In conclusion, naturally occurring allelochemicals of S. violaceum not only inhibit the plant growth but also suppress the hepatitis B virus. |
