H2 S in Horticultural Plants: Endogenous Detection by an Electrochemical Sensor, Emission by a Gas Detector, and Its Correlation with L-Cysteine Desulfhydrase (LCD) Activity

Abstract

H2 S has acquired great attention in plant research because it has signaling functions under physiological and stress conditions. However, the direct detection of endogenous H2 S and its potential emission is still a challenge in higher plants. In order to achieve a comparative analysis of the content of H2 S among different plants with agronomical and nutritional interest including pepper fruits, broccoli, ginger, and different members of the genus Allium such as garlic, leek, Welsh and purple onion, the endogenous H2 S and its emission was determined using an ion-selective microelectrode and a specific gas detector, respectively. The data show that endogenous H2 S content range from pmol to µmol H2 S · g−1 fresh weight whereas the H2 S emission of fresh-cut vegetables was only detected in the different species of the genus Allium with a maximum of 9 ppm in garlic cloves. Additionally, the activity and isozymes of the L-cysteine desulfhydrase (LCD) were analyzed, which is one of the main enzymatic sources of H2 S, where the different species of the genus Allium showed the highest activities. Using non-denaturing gel electrophoresis, the data indicated the presence of up to nine different LCD isozymes from one in ginger to four in onion, leek, and broccoli. In summary, the data indicate a correlation between higher LCD activity with the endogenous H2 S content and its emission in the analyzed horticultural species. Furthermore, the high content of endogenous H2 S in the Allium species supports the recognized benefits for human health, which are associated with its consumption.