Sri Lanka’s traditional medicinal system, with a rich history spanning over 3000 years, remains
a trusted and widely used form of healthcare among people. Recently, Morinda citrifolia (commonly known as Noni) has gained attention in scientific studies for its potential in preventing and treating various illnesses, specifically cancers. In Sri Lanka, however, there have been limited in vitro investigations on its composition and antioxidant capacity. This study aimed to explore the antioxidant activity, total phenolic content, and total flavonoid content of methanolic extracts obtained from different parts of the Morinda citrifolia (M. citrifolia) plant, specifically the leaves and fruits grown in Sri Lanka. Antioxidant capacity was assessed using the 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay and the oxygen radical absorbance capacity (ORAC) assay. The Folin-Ciocalteu method and the aluminum chloride colorimetric method were used to quantify total polyphenols and flavonoids, respectively. The findings show that both the leaves and fruits of M. citrifolia are rich sources of antioxidants when compared with Trolox as the reference standard. Notably, M. citrifolia leaves exhibited higher levels of total phenolic content (0.519 ± 0.09 GAE/g) and total flavonoid content (6.943 ± 1.22 QE/g), along with stronger antioxidant activity as indicated by a lower IC₅₀ value (15.48 μg/mL), compared to the fruits, which recorded a total phenolic content of 0.483 ± 1.8 GAE/g, total flavonoid content of 1.79 ± 0.12 QE/g, and a higher IC₅₀ value (28.90 μg/mL). Similarly, ORAC assay results confirmed that the leaves have superior antioxidant potential with higher ORAC value (67.06 ± 15.9) relative to the fruits (48.85 ± 9.7). Given these results, promoting the use of M. citrifolia products, especially those derived from leaves, could be beneficial in Sri Lanka.
Keywords: Morinda citrifolia, Methanolic extraction, Antioxidants, Sri Lanka, Total phenolic content
