Alkyl- and Alkenylresorcinols of Wheat Grains and their Chemotaxonomic Significance

The Role of Resorcinolic Lipids of Caryopsis Surface in the Process of Cereal Infection by Rhizoctonia solani and Fusarium culmorum

Cereal caryopses are rich in 5-n-alk(en)ylresorcinols, antimicrobial compounds. In this paper, the correlation between the presence of resorcinolic lipids on the surface of cereal grains and the susceptibility of their seedlings to infection by Rhizoctonia solani or Fusarium culmorum was evaluated. The declines in length of both the roots and coleoptiles were observed in barley seedlings of Scarlett and Rabel cultivars grown from the wax-impoverished seeds infected with F92 and F93 strains of Rhizoctonia solani, respectively. Regarding wheat, R. solani F93 significantly reduced only the coleoptile growth. Resorcinolic lipids, being the mixture of homologues with C17–C25 carbon chains, were the only compounds washed off wheat caryopses by chloroform. Moreover, the better anti-Rhizoctonia solani F93 activity of 5-n-alk(en)ylresorcinols of wheat grains than that of rye caryopsis lipids was proven by the poisoned medium technique. Two saturated homologues (C21:0 and C23:0) were the most effective inhibitors of the mycelial growth of this fungus. Thus, the susceptibilities of barley and wheat seedlings to some fungal pathogens have been found to be related to the content and composition of 5-n-alk(en)ylresorcinols in the waxy layer of cereal grains, confirming the protective role of these compounds, during the early stages of cereal development.

Monitoring of changes in 5-n-alkylresorcinols during wheat seedling development

For seven days of wheat growth, caryopsis remained the main source of 5-n-alkylresorcinols with C19 and/or C21 homolog as a main compound. Shoot contained small amount of these phenolic lipids; their average content was 3.23% of level obtained in the whole seedling. Moreover, 41.38% of resorcinolic lipids of seven-day-old shoot was accumulated in part of leaf covered by coleoptile. Interestingly, a removal of 1.07% of the primary pool of kernel alkylresorcinols by short-term washing (10 s) of wheat seed with acetone before planting decreased their level only in seed of seven-day old seedling. Compared to the respective controls, this treatment did not affect the amount of these lipids in the green part of seedling that proved that de novo synthesis of 5-n-alkylresorcinols takes place in shoots. The very similar homolog profiles of these lipids in four- and seven-day-old shoots turned out to be markedly less diversified than those found in respective seed samples. Compared to the mature wheat caryopsis, the rise in the content of very-long-chain homologs was observed only in the oldest shoot. Their increased accumulation was probably connected with formation of cuticular layer providing the defensive barrier against various phytopathogens.

Characterization and Discrimination of Ancient Grains: A Metabolomics Approach

Hulled, or ancient, wheats were the earliest domesticated wheats by mankind and the ancestors of current wheats. Their cultivation drastically decreased during the 1960s; however, the increasing demand for a healthy and equilibrated diet led to rediscovering these grains. Our aim was to use a non-targeted metabolomic approach to discriminate and characterize similarities and differences between ancient Triticum varieties. For this purpose, 77 hulled wheat samples from three different varieties were collected: Garfagnana T. turgidum var. dicoccum L. (emmer), ID331 T. monococcum L. (einkorn) and Rouquin T. spelta L. (spelt). The ultra high performance liquid chromatography coupled to high resolution tandem mass spectrometry (UHPLC-QTOF) metabolomics approach highlighted a pronounced sample clustering according to the wheat variety, with an excellent predictability (Q²), for all the models built. Fifteen metabolites were tentatively identified based on accurate masses, isotopic pattern, and product ion spectra. Among these, alkylresorcinols (ARs) were found to be significantly higher in spelt and emmer, showing different homologue composition. Furthermore, phosphatidylcholines (PC) and lysophosphatidylcholines (lysoPC) levels were higher in einkorn variety. The results obtained in this study confirmed the importance of ARs as markers to distinguish between Triticum species and revealed their values as cultivar markers, being not affected by the environmental influences.

Dynamics of alkylresorcinols during rye caryopsis germination and early seedling growth

Among secondary metabolites, alkylresorcinols are considered particularly important for the antimicrobial defense system in cereal grains. Dry rye caryopses and young seedlings contain detectable quantities of resorcinolic lipids. Overall, 11 distinct alkylresorcinol homologues were identified, which showed variable profiles during rye germination and early seedling development, especially with reference to the production of very long homologues and to side chain saturation. Additionally, changes in the alkylresorcinol composition during rye seedling growth are presented for the first time.

Alkylresorcinols in wheat varieties in the HEALTHGRAIN Diversity Screen

The contents of alkylresorcinols (AR) were analyzed in 131 winter wheats, 20 spring wheats, 10 durum wheats, 5 spelt wheats, and 10 early cultivated forms of wheat (5 diploid einkorn and 5 tetraploid emmer), which are part of the HEALTHGRAIN diversity screen. AR were analyzed by gas chromatography (GC), which provides both total contents and relative homologue compositions, as well as with a Fast Blue colorimetric method that provides only total contents but which is fast and easily screens a large number of samples. There was considerable variation in the total AR content analyzed with GC: winter wheat (220-652 microg/g of dm), spring wheat (254-537 microg/g of dm), durum wheat (194-531 microg/g of dm), spelt (490-741 microg/g of dm), einkorn (545-654 microg/g of dm), and emmer wheat (531-714 microg/g of dm). The relative AR homologue composition was different for different types of wheat, with a C17:0 to C21:0 ratio of 0.1 for winter, spring, and spelt wheats, 0.04 for einkorn and emmer wheat, and 0.01 for durum wheat. The total AR content analyzed with the Fast Blue method was lower than that analyzed with GC but there was a good correlation between the two methods (R(2) = 0.76).

Alkylresorcinols in selected Polish rye and wheat cereals and whole-grain cereal products

The alkylresorcinol content and homologue composition in selected Polish rye and wheat cultivars and selected whole-grain cereal products were determined in this study. Cereal grains and whole-grain cereal products were extracted with acetone, whereas bread types were extracted with hot 1-propanol. The average alkylresorcinol content in tested rye (approximately 1100 mg/kg DM) and wheat (approximately 800 mg/kg DM) grains harvested in Poland was within the range previously reported in Swedish and Finnish samples. The total alkylresorcinol content in tested cereal products available on the Polish market varied from very low levels in barley grain-based foods up to 3000 mg/kg DM in wheat bran. The total alkylresorcinol content in 14 bread samples extracted with hot 1-propanol varied from approximately 100 mg/kg DM in whole bread made with honey up to approximately 650 mg/kg DM in whole-rye bread. Calculated ratios of C17:0 to C21:0 homologues, a useful parameter previously used to distinguish between rye and wheat cereals and their derived products, was about 1.2-1.4 in rye products, about 0.2 in wheat products, and varied between 0.2 and 0.6 in cereal-derived products containing a mixture of whole rye and/or wheat. The data set obtained were subsequently compared using cluster and principal component analysis, which allowed the tested cereal products to be classified into two major groups consisting of whole-rye or whole-wheat products, respectively. On the basis of that approach, mixed cereal products containing rye and wheat bran or whole rye and wheat flour were grouped between those two well-defined clusters. Our work not only provides a detailed examination of alkylresorcinols in selected Polish rye and wheat cultivars and selected whole-grain cereal products, but also demonstrates that this type of analysis accompanied by the use of proper statistical algorithms offers an objective way to evaluate the quality of whole-grain rye and/or wheat and their derived products.

Typing of Histoplasma capsulatum strains by fatty acid profile analysis

The performance of fatty acid profiling for strain differentiation of Histoplasma capsulatum was assessed. Total fatty acids were isolated from the yeast-phase cells of seven stock and two previously unreported clinical strains of H. capsulatum var. capsulatum, as well as from one unreported clinical strain and one stock strain of H. capsulatum var. duboisii, and one strain of each of three other dimorphic zoopathogenic fungal species, Blastomyces dermatitidis, Paracoccidioides brasiliensis and Sporothrix schenckii. Different colony morphology and pigmentation types of the H. capsulatum strains were also included. The most frequently occurring fatty acids were oleic, palmitic, stearic and linoleic acids. There were variations in the relative percentage fatty acid contents of H. capsulatum strains that could be used for strain identification and discrimination. Differentiation between H. capsulatum strains was achieved by the comparison of detected fatty acids accompanied by principal component analysis using calculated Varimax-rotated principal component loadings. Statistical analysis yielded three major principal components that explained over 94 % of total variance in the data. All the strains of H. capsulatum var. capsulatum RFLP classes II and III were grouped into two distinct clusters: the heterogenic RFLP class I formed a large, but also well-defined group, whereas the outgroup strains of H. capsulatum var. duboisii, B. dermatitidis, P. brasiliensis and S. schenckii were shifted away. These data suggest that fatty acid profiling can be used in H. capsulatum strain classification and epidemiological studies that require strain differentiation at the intraspecies level.