Ergosterol contents in mycorrhizal wild edible mushrooms: comparison by hierarchical cluster analysis
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Foundation for Science and Technology (FCT, Portugal) and
COMPETE/QREN/EU for the financial support of this work (research project
PTDC/AGR-ALI/110062/2009) and to CIMO (strategic project PEst-
OE/AGR/UI0690/2011). J.C.M. Barreira also thanks to FCT, POPH-QREN and FSE for
his grant SFRH/BPD/72802/2010.
Sterols are important molecules of the unsaponifiable fraction in several matrices. In
mushrooms, ergosterol, which is an important vitamin D2 precursor, is clearly the main
sterol. Hierarchical cluster analysis (HCA) is an unsupervised learning method to
standardized data, checking for similarities between sample groups. This method
calculates the distances (or correlation) between all samples using a defined metric such
as squared Euclidean distance or Chebychev distance. Hierarchical clustering is the
most common approach in which clusters are formed sequentially. The most similar
objects are first grouped, and these initial groups are merged according to their
similarities. Eventually as the similarity decreases all subgroups are fused into a single
cluster. Herein, ergosterol was quantified by high performance liquid chromatography,
coupled with an ultraviolet detector, in some of the most appreciated mycorrhizal edible
mushrooms (Amanita caesarea, Boletus edulis, Cantharellus cibarius, Lactarius
deliciosus and Morchella esculenta). Considering fat content (percentage) and
ergosterol contents in mg/g fat and mg/100 g of dry weight, two main groups were
formed in the HCA: one aggregating A. caesarea and B. edulis and another constituted
by C. cibarius, L. deliciosus and M. esculenta. These two groups derived from the
higher contents presented by B. edulis and A. caesarea. The detected values indicate
that mushrooms might act as a potential source of this vitamin D2 precursor, with
special relevance for diets deprived of food products of animal origin.
