Sorbicillinoids are a class of fungal metabolites with a cyclic hexaketide nucleus, which contains a typical or modified sorbyl sidechain. These natural products possess bioactivities, such as cytotoxic, antibiotic, antiviral, and lipid-lowering properties.

Although most sorbicillinoids have originated from terrestrial fungi, marine-derived fungi have proved to be a promising source of derivatives. It is noted that sorbicillinoid-bearing marine fungi are distributed widely, from shallow water to deep sea environments.

Among the marine-derived analogs, marine sponge-associated fungi are recognized to produce diverse sorbicillinoid derivatives with unique scaffolds. Sorbifuranones A–C from the sponge-derived fungus Penicillium chrysogenumare a novel class of intriguing sorbicillinol-derived metabolites.

JBIR-59, a dimer of sorbicillinol that lacks a sorbyl sidechain, has antioxidant effects and is produced by the sponge-derived fungus P. citrinum, while a group of novel sorbicillinoid polyketide derivatives was isolated from the Caribbean sponge Agelas dispair-associated fungus Trichoderma sp. 

Sorbicillinoid-bearing marine fungi

Sorbicillinoid alkaloids were first found from a sponge-derived P. chrysogenum strain, and vertinoid polyketides with unique scaffolds were isolated from the sponge-associated fungus T. longibrachiatum. These findings demonstrate that sponge-associated fungi are a rich source of structurally unique sorbifuranones.

Vancomycin-resistant enterococci (VRE) have emerged as important hospital-acquired pathogens in immunosuppressed patients and are increasing steadily in occurrence.

Antimicrobial therapy is problematic for all VRE, posing serious risks to the health of current and future patients. It is urgent to discover new natural antibiotics to overcome these drug-resistant pathogens.

In the course of our search for antibacterial natural products derived from sponge-associated fungi, the marine fungus Trichoderma saturnisporum, which was isolated from the sponge of Dictyonella incise, showed a diverse chemical profile in its HPLC fingerprint and exerted antibacterial effects.

This fungal species has rarely been chemically examined, with only one publication reporting peptaibols, namely Paracelsus A–E. Several Trichoderma species from terrestrial ecosystems have been registered as biocontrol agents to control fungal plant diseases.

The fungus T. saturnisporum is an unexploited species for the biocontrol of fungal diseases of plants, and it is a potential antagonist against important plant pathogens. However, the chemical and biological properties of the marine-derived T. saturnisporum are unexplored and rarely described.

In the present work, they describe the structural elucidation of eight new sorbicillinoid-based derivatives from the sponge Dictyonella incisa-associated fungal strain T. saturnisporum and their antibacterial effects.