Daldinia sacchari (Hypoxylaceae) from India produces the new cytochalasins Saccalasins A and B and belongs to the D. eschscholtzii species complex

Abstract

Stromata of a Daldinia species were collected from half-burnt sugarcane stalks in South India. Based on a combination of morphological and chemotaxonomic evidence, the species was identified as the first recent record of Daldinia sacchari. While it was impossible to obtain cultures from the ascospores, the stromata were subjected to DNA extraction and DNA sequencing and secondary metabolites were analyzed by high-performance liquid chromatography coupled with diode array and mass spectrometric detection (HPLC-DAD/MS). The fruiting body extract was subjected to preparative HPLC for the isolation of secondary metabolites. Two new cytochalasins, for which we propose the trivial names saccalasins A and B, were elucidated besides two known cytochalasins and binaphthalene tetrol (BNT) by NMR spectroscopy and mass spectrometry. Whereas sequencing of housekeeping genes from the stromatal DNA unfortunately failed, an ITS DNA sequence was obtained from this species for the first time and compared to those of related Hypoxylaceae in a phylogenetic tree. The results indicate a close relationship of D. sacchari to the D. eschscholtzii complex, from which cytochalasins are also known as predominant stromatal metabolites. Phylogenetic analyses based on the ITS-rDNA barcode (which can only discriminate the Hypoxylaceae and other Sordariomycetes into species groups, rather than serve as a means of genus or species discrimination) confirmed that D. sacchari belongs to the D. eschscholtzii species complex. However, as with the majority of tropical Hypoxylaceae species, the availability of cultures that can be used to generate DNA sequence data that are more conclusive than ITS will be imperative to further narrow down the phylogenetic affinities of these fungi.