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Glucosinolates in mustard leaves (Brassica juncea L.) and seeds (Brassica nigra L.) were investigated via chemical analysis of their major components and the activity of their hydrolysis products. High-performance liquid chromatography (HPLC) revealed that raw seeds have the highest amount of glucosinolates among the samples tested. Boiling of mustard leaves for 15 minutes significantly reduced the total glucosinolate content (10.94 mmol/g) to up to ~80% in comparison with the raw sample (54.31 mmol/g) which is attributed to thermal degradation of glucosinolates or leaching out to the boiling medium. Similarly, roasting of mustard seeds resulted in a marked decline in total glucosinolate content to 33.70 µmol/g compared with that of raw seed samples (86.18 µmol/g) due to thermal degradation. Liquid chromatography-mass spectrometry (LC-MS) revealed that sinigrin (allyl glucosinolate) is the major glucosinolate in mustard leaves, while the seeds contain sinigrin and gluconapin. Allyl isothiocyanate was identified as the major hydrolytic product using gas chromatography-mass spectrometry (GC-MS). The amount of isothiocyanates were quantified via cyclocondensation reaction and HPLC analysis. Boiling of leaves and roasting of seeds have no significant effect on the total isothiocyanate in comparison with the raw samples. However, the amount of isothiocyanates increases upon hydrolysis in the presence of exogenous myrosinase. Lastly, mustard leaf extracts were found to possess antioxidant properties due to its ability to scavenge free radicals as evidenced by the DPPH assay, which could be attributed to bioactive isothiocyanates inherent in the plant samples.

The effect of storage and heat treatments on the sugar constituents of cassava and yambean roots were investigated using a high performance liquid chromatography (HPLC). Essentially, the total sugar content increased during the first one or two weeks of any 18-28 days storage period. Also, the ratios of fructose and glucose to total sugar content increased, while the ratios of sucrose and inositol decreased. The linamarin content increased markedly in the first 7 days, and continued to increase for several additional days; then it gradually declined and almost disappeared before decay. In yambean root, the three sugars of glucose, fructose and sucrose were found. Although heat treatments by boiling, roasting, and drying all tended to increase the total sugar content of these roots, the linamarin content of cassava roots and of finely-chopped cassava leaves significantly showed a tendency to decrease by such treatments. Investigated at the same time were changes in the constituent pectic substances of these roots. Finally, the changes in appearance occurring in cassave root tissue during storage and heat treatment were observed by a scanning electron microscope (SEM).