Chemical Composition, Antioxidant Potential, and Antimicrobial Activity of Nannorrhops ritchiana (Griff) Aitch

Nannorrhops ritchiana (Griff) Aitch (Arecaceae) is an edible, extensively used shrub to small tree dispersed in Iran, Afghanistan, Pakistan, and Arabian Peninsula. In this study, the total phenolic and flavonoid contents, antioxidant capacity, and antimicrobial activity of the fruit and seed extracts of Nannorrhops ritchiana were evaluated in vitro.

The plant sample was collected from a wild population in Saraydan village, Iranshahr, Sistan and Baluchistan, and the methanolic extracts of the seeds and fruits were obtained by the maceration method The Folin-Ciocalteu and aluminum chloride colorimetric protocols were followed for quantifying total phenolic and flavonoid contents respectively. The total antioxidant and antimicrobial activity of alcoholic extracts were also measured using 2,2-diphenyl-1-picrylhydrazy (DPPH) free radical scavenging assay and disc diffusion method, respectively. Antimicrobial activity was investigated on 5 Gram-positive (Staphylococcus aureus Streptococcus, pneumoniae, Rhodococcus equi, Bacillus subtilis subsp. Spizizenii and Enterococcus faeca) and 3 Gram-negative (Shigella flexneri, Proteus vulgaris, and Salmonella typhi) bacteria, and 3 fungi (Fusarium oxysporum, Aspergillus fumigatus, and Candida albicans).

The total phenolic content of the seeds was higher than that of fruit (331.33±8.3 vs 360.93±10.23 μg gallic acid equivalents/g, respectively) while, the total flavonoid content of seeds was almost half as much as that of fruits (70.50±3.1 vs 127.70 ±5.25 μg quercetin equivalents/g, respectively). The ethanolic seed extract exhibited better scavenging ability for DPPH with IC50 of 117.77 ± 6.3 μg/mL compared to fruit extract with IC50 of 204.34±7.59 μg/mL. Moreover, the ethanolic extracts at initial concentrations inhibited the growth of several tested pathogenic bacterial and fungal strains.

These findings suggest that the fruits and seeds of Nannorrhops ritchiana are rich sources of phenolic compounds with natural moderate antioxidant and antimicrobial properties which can be a candidate for possible dietary and/or medication applications.