600 mg of cowpea leaf tissue from a sample previously ground in liquid nitrogen was homogenized in 5 ml of 5% TCA and centrifuged for 30 min. 2 ml of supernatant was incubated with 2 ml of 0.67% TBA for 30 min at 95°C. The reaction was stopped by cooling on ice for 10 min, then centrifuged for 1 min. The concentration was calculated using lambert-beer law (Extinction coefficient of 155 (1/mM/cm) and I want to express the results in mmol/g fresh weight.