Antioxidant and toxicity tests of roasted noni (Morinda citrifolia) leaf infusion

The antioxidant properties and toxicity profile of roasted noni (Morinda citrifolia L.) leaf infusion were evaluated. The 2,2-diphenylpicrylhydrazyl (DPPH) radical scavenging activity was greater than green tea infusion (81.6 ± 0.9% vs. 57.5 ± 1.8%, P < 0.001). The mean quercetin and kaempferol contents of roasted noni leaf infusion, as prepared by the consumer, were 0.24 ± 0.01 and 0.14 ± 0.01 μg mL⁻¹, respectively. Tannic acid content was 10 ± 1 μg mL⁻¹. The infusion was non-mutagenic in the reverse mutation test in Salmonella typhimurium and did not induce primary DNA damage in E. coli PQ37. Further, no significant primary DNA damage was induced by 5,15-dimethylmorindol, which was the only detectable anthraquinone in noni leaves. The infusion was not cytotoxic in the 24 h brine shrimp toxicity test (LC₅₀ > 1 mg mL⁻¹), nor was there any evidence of acute oral toxicity from the freeze-dried infusion in Sprague-Dawley rats (LD₅₀ > 2000 mg kg⁻¹ b.w.).