Patterns and compound specific stable carbon isotope analysis (δ13C) of capsaicinoids in Cayenne chilli fruits of different ripening stages

Introduction Capsaicinoids are alkaloids of high pungency which are exclusively formed by fruits of the genus Capsicum. Capsaicinoid content and composition of Capsicum fruits are influenced by ripening. Objective Determination of changes in content and pattern of individual capsaicinoids in chilli pods with fruit ripening. Compound specific stable carbon isotope analysis (δ13C values (‰), CSIA) was used for a better understanding of capsaicinoid development during fruit ripening. Methodology Cayenne chillies (Capsicum annuum) were grown in a glasshouse and harvested from different plants at four ripening stages (unripe, semi‐ripe, ripe, overripe). Nine capsaicinoids (one verified by synthesis) were quantified by gas chromatography with mass spectrometry (GC–MS). For CSIA, an acetylation method for derivatising capsaicinoids was developed. Results Variations in the patterns of the nine capsaicinoids were not relatable to a distinct ripening stage and also total contents varied extensively from plant to plant. However, changes in total capsaicinoid concentrations were systematic. In almost all plants, maximum values were reached in unripe fruits, then decreased to semi‐ripe samples and increased again in the following ripening process. Likewise, δ13C values of individual capsaicinoids were always by ~2‰ heavier in unripe than in semi‐ripe or ripe fruits. However, direction of changes in sum‐δ13C values (‰) (taking contributions of all capsaicinoids together) could not be explained by corresponding variations in capsaicinoid concentrations. Conclusions Both quantification and δ13C values (‰) verified the presence of ripening‐related changes in the capsaicinoid content which may be caused by simultaneously proceeding reactions like synthesis, storage and degradation of capsaicinoids. Individual as well as total capsaicinoids were quantified in Cayenne chilli fruits of different ripening stages (from unripe over semi‐ripe to full ripe and overripe) by means of gas chromatography coupled to mass spectrometry. Compound specific stable carbon isotope analysis (δ13C values ‰) of acetylated capsaicinoids verified the presence of ripening‐related changes in capsaicinoid contents. Observed variations in content and stable isotope ratios during fruit ripening and maturation might be ascribed to simultaneously occurring reactions like synthesis, storage and degradation.