RESEARCH ARTICLE Te EuroBiotech Journal 10 | VOLUME 3 ISSUE 1 | JANUARY 2019 Pharmaceutical Biotechnology Abstract Endophytic fungi associated with Nigerian plants have recently generated signifcant interest in drug discovery programmes due to their immense potential to contribute to the discovery of new bioactive compounds. Tis study was carried out to investigate the secondary metabolites of endophytic fungi isolated from leaves of Newbouldia laevis, Ocimum gratissimum, and Carica papaya. Te plants were collected from Agulu, Anambra State, South-East Nigeria. Endophytic fungal isolation, fungal fermentation; and extraction of secondary metabolites were carried out using standard methods. Te crude extracts were screened for antimicrobial activities using the agar well difusion method, and were also subjected to high performance liquid chromatography (HPLC) analysis to identify their constituents. A total of fve endophytic fungi was isolated, two from N. laevis (NL-L1 and NL-L2), one from O. gratissimum (SL-L1), and two from C. papaya (PPL-LAC and PPL-LE2). In the antimicrobial assay, the extracts of NL-L2, SL-L1, and PPL-LE2 displayed mild antibacterial activity against both Gram negative and Gram positive test bacteria. PPL-LAC extract showed mild activity only against S. aureus, while no antimicrobial activity was recorded for NL-L1 extract. All the endophytic fungal extracts showed no activity against the test fungi C. albicans and A. fumigatus. HPLC analysis of the fungal extracts revealed the presence of ethyl 4-hydroxyphenyl acetate and ferulic acid in NL-L1; ruspolinone in NL-L2; protocatechuic acid, scytalone, and cladosporin in SL-L1; indole-3-acetic acid and indole-3- carbaldehyde in PPL-LE2; and indole-3-acetic acid in PPL-LAC. Te fndings of this study revealed the potentials possessed by these plants as source of endophytes that express biological active compounds. Tese endophytes hold key of possibilities to the discovery of novel molecules for pharmaceutical, agricultural and industrial applications. Keywords: Endophytic fungi, Newbouldia laevis, Ocimum gratissimum, Carica papaya, secondary metabolites, antimicrobial activity Introduction Due to the relationships that endophytes seem to have with their host plants, they make a myriad of biologically active compounds. Tese compounds can be classifed as antibiotics, antioxidants, anticancer agents, volatile antimicrobial agents, immunosuppressive compounds, plant growth promoting agents, and insecticides (1). It has been reported that endophytes possess the ability to produce the same or similar chemicals as those originating from their host plants (2, 3). Tis presents endophytic microorganisms as potential alternatives to plants in the search for biologically active molecules. Newbouldia laevis (Bignoniaceae), Ocimum gratissimum (Lamiaceae), and Carica papaya (Caricaceae) are medicinal plants commonly found in Nigeria. Tese plants have been used ethnomedicinally in the treatment of several disease conditions including ulcers, burns, diarrhea, bleeding, haemorrhoids, dysentery, abdominal pains, cough, colds, pruritus, stress, headache, pneumonia, conjunctivitis, diabetes mellitus, epilepsy and convulsions (4-12). Various scientifc studies have shown that N. Laevis possesses antimicrobial, antidiabetic, antioxidant, and antimalarial activities (11-14). O. gratissimum has been reported to show antidiabetic, antioxidant, anxiolytic, sedative, anti-infammatory, hepatoprotective, antitumor, gastroprotective, hypolipidemic, insecticidal, nematicidal, 1 Department of Pharmaceutical Microbiology and Biotechnology, Faculty of Pharmaceutical Sciences, Nnamdi Azikiwe University, Awka, Nigeria 2 Department of Pharmaceutical and Medicinal Chemistry, Faculty of Pharmaceutical Sciences, Nnamdi Azikiwe University, Awka, Nigeria 3 Department of Pharmaceutics and Pharmaceutical Technology, Faculty of Pharmaceutical Sciences, Enugu State University of Sciences and Technology, Enugu, Nigeria *Corresponding author: P. M. Eze E-mail: ezep2004@hotmail.com DOI: 10.2478/ebtj-2019-0002 © 2019 Authors. Tis work was licensed under the Creative Commons Attribution- NonCommercial-NoDerivs 4.0 License. Screening of metabolites from endophytic fungi of some Nigerian medicinal plants for antimicrobial activities Peter M. Eze 1 *, Joy C. Nnanna 1 , Ugochukwu Okezie 1 , Happiness S. Buzugbe 1 , Chika C. Abba 2 , Chidimma R. Chukwunwejim 3 , Festus B. C. Okoye 2 and Charles O. Esimone 1