Background : Kenaf (Hibiscus cannabinus L.) is a member of the malvaceae family and has been prescribed in traditional folk medicine in Africa and India. It showed broad biologicas activities such as hepatoprotective activity, antioxidative activity and haematinic activity. Kenaf leaves contain a lot of vegetable calcium, protein, iron and vitamins, so have high potential as functional food. Thus, the present study purposed to analyze useful substances contained in kenaf leaves and their activities and look for their possibilities as the materials of food and medicine. Methods and Results :　We sowed the seeds of three varieties of kenaf, namely, Dowling, Everglade-41 and Tainung-2 at planting space of 20 × 20㎝ on the field and collected plants on the 98th , 127th and 141st days from sowing. The total polyphenol content was measured using a slightly modified Folin-Denis method, which uses the phenomenon that a phenolic substance turns blue by reaction with phosphomolybdate. Conclusion : We analyzed SOD enzyme activity related to the scavenging of superoxide anion radical (․O2-) through NBT reduction. As for the SOD activity of leaf extract by variety, the activity was 92.6%, 91.0% and 92.6%, respectively, in Tainung-2 on day 98, 127 and 141 from sowing, slightly higher than those in the other two varieties but not significantly different. The activity was slightly higher in the middle period of growth than in the harvest period, but not much different according to harvest time. As for the DPPH radical scavenging activity of leaf extract by variety, the activity was 80.87% and 80.71%, respectively, in Tainung-2 on day 98 (30th of October)and day127 (28th of September), slightly higher than the other two varieties.

To identify salt-tolerance characteristics of corn seedling was treated in solution of 0, 50 and 100 mM NaCl of hydroponic cultivation. In photosynthesis of corn seedling, there was no large difference between 50mM and 0 mM NaCl solution, however, in 100 mM NaCl solution, the tolerance gradually decreased to 76~%,~;49~%,~;and~;31~% after one day, four days, and seven days, respectively, in comparison to 0 mM NaCl solution. Osmotic potential of corn in seedling period was significantly decreased with increasing saline level, however, free proline content in the plant on the ground was significantly increased with increasing saline level and with the lapse of time. In terms of correlation among major characteristics, there was a highly significant positive difference between osmotic pressure potential and photosynthesis, However, highly negative correlation was found between osmotic pressure potential and free proline content. In addition, it was expected that young seedling of corn with saline tolerance may be utilized in the transplantation in salt-accumulated land. Based on above-shown result, in terms of saline tolerance of Chalok-2 variety, growth suppression was serious with 100mM NaCl solution. However, growth was expected that seedling growth would be favorable under 50 mM NaCl solution.