紅藻源真菌株Acremonium sp. NTU492之活性成分研究

Abstract

本研究利用病原菌篩選平臺（Staphylococcus aureus, Escherichia coli, Candida albicans 和 Cryptococcus neoformans）篩選出具有抗菌潛力的海藻源真菌菌株。實驗結果顯示，Acremonium sp. NTU492之粗萃物具有抗Candida albicans 和 Cryptococcus neoformans的效果。因此選擇以頂孢黴菌Acremonium sp. NTU492為目標真菌，以1/2 PDA液態培養與糙米固態培養之後，分離並純化此株真菌的二次代謝物。共計獲得15個化合物，藉由各種光譜資料解析其結構。其中9個為新化合物，分別為acrepeptins A−E（2−6）、acremonisins A−B（12−13）、(4R, 7R, 9S, E)-4,7-dihydroxy-9-propyl-2,3,4,7,8,9-hexahydro-2H-oxecin-1-one（14）、4,4-dihydroxy-6,8-dimethoxy-5-methylisochroman-1-one（15）。另外6個為已知化合物，分別為8-deoxy-trichothecin（1）、cyclo[L-alanyl-L-threonyl-(2S)-2-hydroxy-3-methylbutanoyl-L-isoleucyl-(2S)-2-hydroxy-3-methylbutanoyl]（7）、β-alanine, N-[N-[N-[N-[1-(2-hydroxy-4-methyl-1-oxopentyl)-L-prolyl]-L-isoleucyl]-N-methyl-L-valyl]-N-methyl-L-alanyl]（8）、guangomides A−B（9−10）和brefeldin A（11）。在抗菌活性上，8-deoxy-trichothecin（1）具有抑制白色念珠菌（C. albicans）、新型隱球菌（C. neoformans）的活性，其最小抑制濃度（MIC）分別為2.0和0.5 μg/mL；brefeldin A（11）具有抑制白色念珠菌的活性，其最小抑制濃度（MIC）為32 μg/mL；(4R, 7R, 9S, E)-4,7-dihydroxy-9-propyl-2,3,4,7,8,9-hexahydro-2H-oxecin-1-one（14）具有抑制新型隱球菌的活性，其最小殺真菌濃度（MFC）為16 μg/mL。在抗癌活性上，8-deoxy-trichothecin（1）對於人類肝癌細胞（hepatocellular carcinoma cells，SK-Hep-1）與人類抗藥性卵巢癌細胞（paclitaxel-resistant ovarian cancer cells，TOV-21G-RT）具有毒殺活性，其半抑制濃度（IC50）分別為2.1與1.8 μM；cyclo[L-alanyl-L-threonyl-(2S)-2-hydroxy-3-methylbutanoyl-L-isoleucyl-(2S)-2-hydroxy-3-methylbutanoyl]（7）對於人類肝癌細胞與人類前列腺癌細胞（prostate cancer cells，PC-3）具有毒殺活性，其半抑制濃度（IC50）分別為3.7與6.6 μM；brefeldin A（11）對於人類肝癌細胞與人類前列腺癌細胞（prostate cancer cells，PC-3）具有毒殺活性，其半抑制濃度皆小於1 μΜ；(4R, 7R, 9S, E)-4,7-dihydroxy-9-propyl-2,3,4,7,8,9-hexahydro-2H-oxecin-1-one（14）對於人類肝癌細胞與人類前列腺癌細胞具有毒殺活性，其半抑制濃度分別為1.6與1.7 μM。最後，在抗發炎活性上，acrepeptins A−C（2−4）具有抑制NO產生的活性，於20 μM下抑制NO產生之比例分別為73.3％、58.6％和77.2％。總而言之，本研究共計分離純化15個化合物，並對其結構、化學特性與生物活性進行探究。

In this study, a number of alga-derived fungal strains were isolated from marine algae collected from northeastern coast of Taiwan. In the preliminary antimicrobial screening against bacteria and fungi, including Escherichia coli, Staphylococcus aureus, Candida albicans and Cryptococcus neoformans, the ethyl acetate extracts of liquid (potato dextrose broth) and solid (brown rice) fermented products of Acremonium sp. NTU492, a fungus derived from the red alga Mastophora rosea, were found to exhibit significant growth inhibitory activity against C. albicans and C. neoformans. A series of fractionation and separation was thus undertaken, which has resulted in the isolation and purification of 15 compounds, and their structures were elucidated by spectral analysis. Among these, nine novel compounds included acrepeptins A−E (2−6), acremonisins A−B (12−13), (4R, 7R, 9S, E)-4,7-dihydroxy-9-propyl-2,3,4,7,8,9-hexahydro-2H-oxecin-1-one（14）and 4,4-dihydroxy-6,8-dimethoxy-5-methylisochroman-1-one (15). The other were known compounds, determined to be 8-deoxy-trichothecin (1), cyclo[L-alanyl-L-threonyl-(2S)-2-hydroxy-3-methylbutanoyl-L-isoleucyl-(2S)-2-hydroxy-3-methylbutan -oyl] (7), β-alanine, N-[N-[N-[N-[1-(2-hydroxy-4-methyl-1-oxopentyl)-L-prolyl]-L-isoleucyl]-N-methyl-L-valyl]-N-methyl-L-alanyl] (8), guangomide A (9), guangomide B (10) and brefeldin A (11). In terms of antibacterial activity, 8-deoxy-trichothecin (1) showed activity against Candida albicans and Cryptococcus neoformans with MIC = 2.0 μg/mL and 0.5 μg/mL, respectively; brefeldin A（11）showed activity against Candida albicans with MIC = 32 μg/mL; (4R, 7R, 9S, E)-4,7-dihydroxy-9-propyl-2,3,4,7,8,9-hexahydro-2H-oxecin-1-one（14）showed activity against Cryptococcus neoformans with MFC = 16 μg/mL. In respect of anticancer activity, 8-deoxy-trichothecin (1) showed activity against hepatocellular carcinoma cells (SK-Hep-1) and paclitaxel-resistant ovarian cancer cells (TOV-21G-RT), with IC50 = 2.1 and 1.8 μM, respectively; cyclo[L-alanyl-L-threonyl-(2S)-2-hydroxy-3-methylbutanoyl-L-isoleucyl-(2S)-2-hydroxy-3-methyl butanoyl] (7) showed activity against hepatocellular carcinoma cells and prostate cancer cells (PC-3), with IC50 = 3.7 and 6.6 μM respectively; brefeldin A（11）showed activity against hepatocellular carcinoma cells and prostate cancer cells with both IC50 lower than 1 μΜ; (4R, 7R, 9S, E)-4,7-dihydroxy-9-propyl-2,3,4,7,8,9-hexahydro-2H-oxecin-1-one（14）showed activity against hepatocellular carcinoma cells and prostate cancer cells with IC50 = 1.6 and 1.7 μM respectively. Finally, in regard to anti-inflammatory activity, acrepeptin A−C (2−4) inhibited 73.3, 58.6 and 77.2％ of NO production under the concentration of 20 μM. In summary, a total of 15 compounds were isolated, and their structures, chemical properties and biological activities were investigated in this study.