Structurally Various Sorbicillinoids From an Endophytic Fungus Acremonium citrinum SS-g13

Abstract

Three new sorbicillinoids, including trimer trisorbicillinone E (1), acremosorbicillinoids A and B (2 and 3), and a new alkaloid acremokaloid A (4), and a new natural product 2S,3S-acetyl-β-methyltryptophan (5), were isolated from an endophytic fungus Acremonium citrinum SS-g13, which is found in Fructus mori plant root. In addition, eight known sorbicillinoids (6–13) were also obtained. The new compound structures were established using NMR, HRESIMS spectra, and reported spectroscopic data. The absolute configurations of compounds 1–5, were determined by spectroscopic analysis, Snatzke’s method, and time-dependent density functional theory-electronic circular dichroism (TDDFT-ECD) calculations. Compound 11 exhibited significant cholesterol efflux enhancing activity. A plausible biosynthesis pathway for the sorbicillinoids is discussed.

Major Facilitator Superfamily Transporter Participates in the Formation of Dimeric Sorbicillinoids Pigments

“…Cluster 320.1 harbors a pair of PKSs, a hr-PKS (StaC) and a nr-PKS (StaB), which are presumably responsible for the formation of sorbicillin monomer (1). A FAD-dependent monooxygenase (StaF), which shares 64.4 and 65.9% sequence similarity with TrSorC and PcSorC, respectively, is proposed to stereoselectively oxidize sorbicillin (1) to sorbicillinol (2). Surprisingly, this BGC does not encode any TrSorD or PcSorD homology genes (Table 1).…”

“…SorA is a highly reducing (hr) PKS 18 that is responsible for the formation of a reduced triketide intermediate, which is then extended by the nonreducing (nr) PKS 19 SorB to form sorbicillin (1). SorC, a FAD-dependent monooxygenase, then oxidatively dearomatizes sorbicillin (1) to form a reactive intermediate sorbicillinol (2).…”

“…Sorbicillinoids are common fungal pigments produced by many terrestrial − and marine fungi. − Recently, our group developed a PMG (phenotype combined with metabolomic and genomic) strategy to isolate novel fungal pigments and successfully identified several sorbicillinoid pigments from the sponge-derived fungus Stagonospora sp. SYSU-MS7888 .…”

Recent Advances in Chemistry and Bioactivities of Secondary Metabolites from the Genus Acremonium

“…A chemical investigation of the terrestrial plant Fructus mori derived A. citrinum SS-g13 produced three new sorbicillinoids, trisorbicillinone E (100), acremosorbicillinoids A and B (101 and 102), and one new natural product, 2S,3S-acetyl-β-methyltryptophan, along with eight known sorbicillinoids. Among them, dihydrobisvertinolone showed significant cholesterol efflux-enhancing activity [44].…”

“…Two new alkaloids, acremokaloid A (114) and 2S, 3S-acetyl-β-methyltryptophan (115), were isolated from an endophytic fungus A. citrinum SS-g13 [44] (Figure 12). Moreover, a known compound, β-Adenosine, was obtained from the mangrove-derived fungus A. citrinum MMF4 [37].…”