GC–MS Characterization of Bioactive Compounds of Endophytes <i>Colletotrichum siamense</i> Strain 67 and <i>Meyerozyma guilliermondii</i> CBS 2077 From <i>Stevia rebaudiana</i> (Bertoni) Bertoni

ABSTRACT Endophytic microbes are increasingly recognized as a source of structurally diverse metabolites with applications in biotechnology, medicine, and agriculture. The secondary metabolite profiles of two endophytic isolates, Colletotrichum siamense strain 67 and Meyerozyma guilliermondii CBS 2077, were characterized using GC–MS. More than 80% of the entire peak area of C. siamense was typically 2,3‐butanediol, with minor elements such as chromones, fatty acid esters, coumarin derivatives, and ergosterol analogs also present. These metabolites are associated with antibacterial activity, antioxidant properties, and the promotion of plant development, primarily supporting host defense and ecological interactions. A wider range of bioactive substances, such as benzodiazole derivatives, chromones, long‐chain hydrocarbons, and pharmacologically significant metabolites like actinomycin C2 and didemnin B, were present in M. guilliermondii , despite sharing 2,3‐butanediol as a primary constituent. The identification of these strong antibiotics and anticancer drugs demonstrate distinct metabolic adaptability and possible pharmacological significance. M. guilliermondii synthesizes both growth‐promoting and pharmacologically active metabolites, whereas C. siamense primarily specializes in growth‐promoting volatiles. The functional diversity of endophytic microorganisms and their potential as sources of new bioactive chemicals are highlighted by these findings. Further potential uses in medication development and sustainable agriculture needs more purification, structural clarification, and biological testing.