海洋綠藻源真菌株 Aspergillus sp. NTU967 之成分研究

Abstract

本研究利用抑制金黃色葡萄球菌 (Staphylococcus aureus) 和新型隱球菌(Cryptococcus neoformans) 的活性為篩選平台，針對從基隆八斗子所採集的海藻分離出之343株藻源真菌株，進行了初步的抑菌活性測試。結果發現由石蓴 (Ulva lactuca) 單離出之衍生真菌株Aspergillus sp. NTU967的PDY (Peptone, Dextrose, Yeast Extract) 發酵培養液，以及使用發芽糙米培養的萃取液，皆具有明顯的抑菌效果。接著以PDY液態培養基與發芽糙米進行大量培養，針對其發酵液所含之代謝產物進行分析、分離與純化，計獲得13個化合物，藉由各種光譜分析決定其化合物結構。其中有8個為新化合物，分別為aspergilsmins A − H (1 − 7和13)，另外5個為已知化合物，分別為clavatol (8)、deoxytryptoquivaline (9)、tryptoquivaline (10)、quinadoline B (11) 和 (4-oxo-5,6-dihydro-4H-pyran-3-yl)-acetic acid (12)。後續在各種活性平台的評估上，得知aspergilsmins E (5) 和F (6) 具最佳的抑菌活性，對於金黃色葡萄球菌 (Staphylococcus aureus) 的最小抑菌濃度 (MIC) 皆為32 μg/ml；在抑制人類前列腺癌細胞 (Prostate cancer cells; PC-3) 和人類肝癌細胞 (hepatocellular carcinoma cells; SK-Hep-1) 上，aspergilsmin C (3) 具有顯著的效果，其半抑制濃度 (IC50) 分別為7.3 ± 0.3和 2.7 ± 0.2 μM；所有化合物對於小鼠神經膠質BV-2細胞皆不具顯著抑制NO產生的活性。對於化合物3的抗癌細胞毒性詳細作用機制，仍有待進一步實驗證實。

Among the mairne microorganisms, marine-derived fungi are able to produce lots of secondary metabolites with highly structural diversity. The discovery of new natural products from marine-derived fungi has increased dramatically over the last few decades, and some of them revealed great potentials for drug developments. In our preliminary screening, the bioactivities of 343 fungal strains, isolated from marine macroalgae collected from northeast coast of Taiwan, were tested intensively. Of these, the ethyl acetate extract of the fermented broth of Aspergillus sp. NTU967, isolated from a marine green alga Ulva lactuca, was found to exhibit significant antimicrobial activities against Staphylococcus aureus and Cryptococcus neoformans. Therefore, bioassay-guided separations of the active principles from liquid- or solid-state fermentations of Aspergillus sp. NTU967 were carried out, and which have led to isolation and purification of compounds 1 – 13 . Their structures were elucidated by spectroscopic analysis to be eight new aspergilsmins A − H (1 − 7 and 13), together with five previously reported clavatol (8), deoxytryptoquivaline (9), tryptoquivaline (10), quinadoline B (11) and (4-oxo-5,6-dihydro-4H-pyran-3-yl)-acetic acid (12). Aspergilsmins E (5) and F (6) exhibited significant growth inhibition against Staphylococcus aureus with the minimum inhibitory concentration (MIC) of 32 μg/ml. Aspergilsmin C (3) showed cytotoxic activity against prostate cancer cells (PC-3) and hepatocellular carcinoma cells (SK-Hep-1), and the half inhibitory concentrations (IC50) were 7.3 ± 0.3 and 2.7 ± 0.2 μM, respectively. The detailed mechanism of compound 3 against cancer cells remains to be confirmed by further experiments.