Isolation and biological activities of 3-hydroxy-4(1H)-pyridone

3-Hydroxy-4(4H)-pyridone (3,4-DHP), a degraded product of mimosine [beta-[N-(3-hydroxy-4-oxypyridyl)]-alpha-aminopropionic acid], is known to cause goiters, loss of hair, and infertility in animals, but limits of 3,4-DHP on separation and purification have prevented efforts on investigating other toxicity and biological properties of 3,4-DHP. By this study, a novel and simple isolation of 3,4-DHP was developed either from Leucaena leaves using an ion-exchanged resin or mimosine degraded in high temperature (110 degrees C, 6 h). The inhibition of mimosine on the growth of barnyardgrass was approximately fourfold higher (IC50 = 0.04 mg g(-1)) than that of 3,4-DHP (IC50 = 0.15 mg g(-1)). In general, the antifungal activity of mimosine is much stronger than that of 3,4-DHP, but it differs depending on the kind of fungi. The 1,1-diphyenyl-2-picrylhydrazyl (DPPH) radical scavenging activity of 3,4-DHP, in contrast with the growth inhibitory activity, is about fourfold stronger [EC50 = 2.4 mg g(-1) gallic acid equivalent (GAE)] than that of mimosine [EC50 = 10.3 mg g(-1) GAE]. This study is the first to report on the herbicidal, antifungal, and antioxidant activities of 3,4-DHP.