Aims: To isolate and identify the bioactive compounds produced by Nocardia levis MK-VL_113.
Methods and results: Cultural characteristics of Noc. levis isolated from laterite soils of Guntur region were recorded on International Streptomyces Project media. Morphological studies of the strain through scanning electron microscopy revealed the clear pattern of its hyphal fragmentation into rod-shaped bacilli. Chemical examination of the secondary metabolites of the strain grown on sucrose-tryptone broth led to the isolation of three fractions active against Bacillus cereus. Further analysis of second fraction resulted in the isolation of two active subfractions. Two different phthalate esters, namely, bis-(2-ethylhexyl) phthalate and bis-(5-ethylheptyl) phthalate, were purified from the first active subfraction, and the structural elucidation of these compounds was confirmed on the basis of FT-IR, mass and NMR spectroscopy. The partially purified second subfraction subjected to Gas Chromatography-Mass spectroscopy contained nine components: decanedioic acid; 2,6-piperdione monooxime; 1-eicosanol; beta-1-arabinopyranoside, methyl; cyclopentaneundecanoic acid; hexadecanoic acid; silane, trichloro eicosyl; 1-hexacosanol; and 1,2-dodecanediol. The antimicrobial activity of the bioactive compounds produced by Noc. levis was expressed in terms of minimum inhibitory concentration.
Conclusions: The present study clearly revealed that the metabolites of Noc. levis act as bioactive compounds against gram-positive and gram-negative bacteria, yeast and filamentous fungi. It also supports the idea that there are a number of rare actinomycetes remained to be explored for new bioactive compounds.
Significance and impact of the study: Metabolites of Noc. levis exhibited antibacterial and antifungal activities. This is the first report of bis-(5-ethylheptyl) phthalate as well as the nine partially purified compounds from actinomycetes. In addition, this is also the first report of bis-(2-ethylhexyl) phthalate from the genus Nocardia.