Abstract:
Rhodomyrtus tomentosa has been used as a traditional medicine for a long time in
Southeast Asia countries and also in Indonesia. It is believed that the phytochemical content of its
fruit at different levels of ripeness may affect its antioxidant activity. Therefore, this study aims to
determine the antioxidant activity, phenols and flavonoids contents, and their distribution in the
leaves and fruits of R. tomentosa at different levels of maturity. The antioxidant activity was
determined using DPPH and FRAP analysis. Furthermore, the total flavonoid and phenolic
contents were analyzed using the colorimetric and Folin–Ciocalteu methods. The distribution of
secondary metabolites in the leaves or fruits tissues was determined using histochemical analysis.
Antioxidant capacity was analyzed using DPPH and FRAP, and a comparable result was
obtained. The highest antioxidant activity was observed in the green fruit with the value of
1419.75 ± 3.48 and 1367.59 ± 9.12 μmol TE/g DW for DPPH and FRAP, respectively.
The highest TFC value observed in the young leaves and green fruits of the ethanol extract
was 96.375 ± 3.96 and 95.731 ± 5.42 mg QE/g DW, respectively. The highest TPC was
found in the red fruits 50.772 ± 7.46 mgAGE/g DW. The histochemical analysis provided a clear
distribution of flavonoid and phenolic within the leaves and fruits. It was found that both
compounds accumulated in the epidermis, mesophyll, vascular bundles, secretory cavity, and
parenchyma midrib of the leaves, and also in the exocarp and mesocarp endocarp, secretory cavity,
vascular bundles, seed, trichomes of the fruits. This study showed that young leaves and green
fruits have a higher potency of being a natural source of antioxidants and flavonoid compounds.
Keywords: antioxidant; flavonoid contents; histochemical analysis; rose myrtle
