Endophytic Diaporthe sp. LG23 Produces a Potent Antibacterial Tetracyclic Triterpenoid

Betulinic Acid, The First Lupane-Type Triterpenoid Isolated from Both a Phomopsis sp. and Its Host Plant Diospyros carbonaria Benoist

Following a biological screening using a dengue replicon virus-cell-based assay, Diospyros carbonaria AcOEt extract was investigated, affording six known lupane-type triterpenoids endowed with anti-DENV-2 NS5 polymerase activity. The study of the associated microbial community of this species permitted us to identify 38 endophytes belonging to five different orders. Nine out of these 38 strains showed significant activity on the dengue replicon assay. The chemical investigation of the most active one, Phomopsis sp. SNB-LAP1-7-32, led to the isolation of betulinic acid, an anti-viral secondary metabolite isolated previously from the host plant. This result is the first example of a lupane-type triterpenoid isolated from both an endophyte and its host plant. Its presence in the Phomopsis strain may result from gene transfer and/or specific niche selection.

Preparation of novel ring-A fused azole derivatives of betulin and evaluation of their cytotoxicity

An efficient scheme to synthesize novel ring-A fused heterocyclic derivatives of betulin was developed. The starting reaction of this synthesis was one-pot selective bacterial oxidation of betulin to betulone used as the key compound to synthesize the substituted azoles such as C(2)-C(3)-fused 1,2,3-triazoles, oxazoles and 1,2,4-triazine, as well as C(1)-C(2)-fused isoxazoles. The semi-synthetic compounds were screened for their cytotoxic activity against human cancer cell lines A549, HCT 116, HEp-2, MS and RD TE32 with use of the photometric MTT assays. Among the tested compounds, N-acetyltriazole of betulin (10) displayed impressive cytotoxic activity with IC₅₀ 2.3-7.5 μM against HCT 116, HEp-2, MS and RD TE32 cell lines as well as 3-methyl-4-oxido-1,2,4-triazine-derivative of betulonic acid (12) that was active against HCT 116 and HEp-2 cell lines with IC₅₀ 1.4 and 1.5 μM, respectively. Comparative experiments showed triazole (10) to have a lower cytotoxicity to normal epithelial cells, in comparison with compound (12). In accord with the in vivo acute toxicity test, the LD₅₀ of triazole (10) exceeded 600 mg/kg. The ability of the most potent active triazole (10) to trigger apoptotic cell death was explored in the Annexin V-FITC test and by analyzing of caspase activity and morphological alterations in mitochondria and nuclei of HCT 116 cells.

Three cyclic pentapeptides and a cyclic lipopeptide produced by endophytic Fusarium decemcellulare LG53

Endophytic Fusarium decemcellulare LG53 harbored in Mahonia fortunei produces three cyclic pentapeptides (1–3) and the cyclic lipopeptide, fusaristatin A (4).