Sulfur-Containing Cytotoxic Curvularin Macrolides from Penicillium sumatrense MA-92, a Fungus Obtained from the Rhizosphere of the Mangrove Lumnitzera racemosa

Sumalarins A–C (1–3), the new and rare examples of sulfur-containing curvularin derivatives, along with three known analogues (4–6), were isolated and identified from the cytotoxic extract of Penicillium sumatrense MA-92, a fungus obtained from the rhizosphere of the mangrove Lumnitzera racemosa. Their structures were established by detailed interpretation of NMR and MS data, and compound 1 was confirmed by X-ray crystallographic analysis. Compounds 1–3 and 5 showed potent cytotoxicity against some of the tested tumor cell lines. Sulfur substitution at C-11 or a double bond at C-10 significantly increased the cytotoxic activities of the curvularin analogues.