Secondary Metabolites Isolated from the Strain Aspergillus terreus

Abstract

Fungi produce a wide variety of secondary metabolites that are of human interest, among them antibiotics, cyclosporines, mevinic acids, alkaloids, and antifungal compounds [1]. In this research we isolated three natural compounds from a strain of Aspergillus terreus collected from “paramo de Guasca (Cundinamarca, Colombia).” The A. terreus was fermented in PGS and Saboraud media at room temperature for 12 days. The biomass obtained (36.5 g) was extracted by the Soxhlet method (hexane, CH2Cl2, EtOAc, and MeOH). The MeOH extract was chromatographed on silica gel 60 G and eluted in a mixture of EtOAc–MeOH 1:1. The mannitol (1) (180 mg) was isolated. The Sabouraud broth fermentation medium (20 L) was treated with hexane, CH2Cl2, and EtOAc. The CH2Cl2 extract was chromatographed on silica gel CC, and from the hexane– EtOAc 1:1 fraction, butyrolactone I (2) (40 mg) and R(–)-6-hydroxymellein (3) (8 mg) were isolated. Mannitol (1) is a white solid crystal with needle-shaped form (MeOH, H2O), mp 167.5 C. The spectral data of 1 agreed with those published earlier in the literature for mannitol [2]. According to the literature, mannitol has been isolated from the mycelium of Aspergillus species and other fungus. These compounds are believed to contribute to osmotic stabilization of cell hyphae and to form endogenous reserves that are metabolized continuously [3]. Butyrolactone I (2). White solid crystal with needle-shaped form (EtOAc, MeOH, and H2O), mp 92 C. UV spectrum (MeOH, max, nm): 203 and 307. PMR spectrum (400 MHz, DMSO-d6, , ppm, J/Hz): 7.52 (2H, d, J = 8.8, H-3, 5), 6.87 (2H, d, J = 8.8, H-2, 6), 6.53 (1H, d, J = 8.0, H-16), 6.48 (1H, dd, J = 8.0, 2.0, H-15), 6.40 (1H, d, J = 2.0, H-19), 5.02 (1H, t, J = 6.4, H-21), 3.74 (3H, s, H-12), 3.37 (2H, s, H-13), 3.00 (2H, d, J = 6.4, H-20), 1.63 (3H, s, H-23), 1.54 (3H, s, H-24). 13C NMR spectrum (100 MHz, D2O, , ppm): 169.59 (C-11), 168.70 (C-9), 156.79 (C-1), 153.09 (C-17), 136.88 (C-8), 133.96 (C-22), 131.59 (C-19), 129.26 (C-5), 129.26 (C-3), 128.97 (C-15), 127.51 (C-7), 124.36 (C-14), 126.25 (C-18), 121.74 (C-21), 121.38 (C-4), 115.75 (C-2), 115.75 (C-6), 114.84 (C-16), 85.63 (C-10), 53.21 (C-12), 38.32 (C-13), 28.85 (C-20), 25.43 (C-23), 17.48 (C-24).