Non-Volatile Metabolites from Trichoderma spp.

The genus Trichoderma is comprised of many common fungi species that are distributed worldwide across many ecosystems. Trichoderma species are well-known producers of secondary metabolites with a variety of biological activities. Their potential use as biocontrol agents has been known for many years. Several reviews about metabolites from Trichoderma have been published. These reviews are based on their structural type, biological activity, or fungal origin. In this review, we summarize the secondary metabolites per Trichoderma species and elaborate on approximately 390 non-volatile compounds from 20 known species and various unidentified species.


Introduction
Trichoderma is a genus of fungi of the family Hypocreaceae. It is distributed in soils worldwide across various habitats [1]. Trichoderma is a valuable resource for structurally novel natural products with diverse bioactivities [2]. Among well-studied fungi, Trichoderma species are known for their ability to produce bioactive secondary metabolites, including polyketides, alkaloids, terpenoids, and peptaibols [3]. Many species have been extensively investigated due to their application as biological control agents [4]. In this article, we reviewed the origin, structure, and bioactivity of non-volatile secondary metabolites from Trichoderma spp. and grouped them per species.

Metabolites from Trichoderma cremeum
A new 10-member lactone, cremenolide (105), was isolated from T. cremeum. In vitro tests showed that cremenolide inhibited the radial mycelium growth of Fusarium oxysporum, B. cinerea, and R. solani, and it significantly promoted tomato seedling growth [19].
In addition, compound 6-pentyl-α-pyrone (67) was also found from T. harzianum T77 and SQR-T037. It is used for the control of grapevine trunk diseases [15], and it effectively controlled F. oxysporum and may control Fusarium wilt in cucumber, in continuously cropped soil [35].
One new compound, trichoderol A (313), was isolated from Trichoderma sp. cultures. Compound 313 was evaluated for antibacterial activity against Pseudomonas putida, Nocardia brasiliensis, and Kocuria rhizophila. The results showed compound 313 had antibacterial activity against the three pathogenic bacteria, with a MIC value of 5 µmol/L [64].
Although Trichoderma spp. have been widely studied, more metabolites will likely be identified in the future.