Variation on charantin contents of various organs and harvest seasons in bitter gourd

The charantin contents of leaves, stems, female and male f lowers, and fruits in bitter gourd (Momordica charantia) were analyzed at different harvest seasons to investigate the availability of potential edible parts other than fruits. The charantin contents of fruits ranged from 14.7 to 16.0 mg∙g^-1 dry weight (DW) and those of leaves ranged from 131.4 to 138.0 mg∙g^-1 DW, which was eight times higher than in fruits. The charantin contents of female and male flowers and stems were also significantly higher than those of the fruits. The ratio of total charantin content was highest in leaves (48%) of DW, followed by female flowers (20-21%), male flowers (14%), stems (12-13%), and fruits (5%). The charantin contents of fruits harvested 14 days after fruit setting was higher in June to mid-July (20.2 to 23.3 mg∙g^-1 DW) than in late July to late August (13.3 to 19.4 mg∙g^-1 DW). The higher the fruit weight, the lower the charantin contents, which showed that a negative correlation exists between fruit weight and charantin contents in bitter gourd. These results suggest that to obtain bitter gourd fruits with high charantin contents, fruits should be harvested until mid-July when fruit growth is fast and temperature is high. In addition, leaves, stems, and female and male flowers of bitter gourd can be used as for food, which are known to reduce blood sugar level.