Phytochemical Analysis, Quantification of Flavonoids and Phenols, and Assessment of Anti-Tubercular Activity of Citrus jambhiri Fruit Peel Extract

Introduction:
Tuberculosis (TB) remains a global health concern, prompting the exploration of natural products for novel therapeutics. Citrus fruit peels, often discarded as waste, are rich in bioactive compounds with potential antimicrobial and antioxidant properties.

Methods:
This study investigated the extraction, phytochemical profiling, and anti-tubercular potential of Citrus jambhiri fruit peel. The dried and powdered peel was extracted by maceration with 95% ethanol for 72 hours at room temperature with intermittent shaking. The extract was filtered and concentrated under reduced pressure to yield a semi-solid residue. Phytochemical screening was performed using standard qualitative tests. Total phenolic content (TPC) was determined by the Folin–Ciocalteu method, where 1 mL of extract (1 mg/mL) was mixed with 5 mL of 10% Folin–Ciocalteu reagent and 4 mL of 7.5% sodium carbonate. After 30 minutes, absorbance was measured at 765 nm, using gallic acid as a standard. Total flavonoid content (TFC) was determined by the aluminium chloride colorimetric assay, mixing 1 mL of extract with 4 mL of distilled water, 0.3 mL of 5% sodium nitrite, 0.3 mL of 10% aluminium chloride, and 2 mL of 1 M sodium hydroxide. Absorbance was measured at 510 nm with quercetin as standard. Anti-tubercular activity was evaluated against Mycobacterium tuberculosis H37Rv using the Microplate Alamar Blue Assay (MABA), with results expressed as minimum inhibitory concentration (MIC).

Results:
The extract showed the presence of alkaloids, flavonoids, tannins, phenols, terpenoids, and saponins. Quantitative analysis revealed TPC of 7.66 mg GAE/g and TFC of 10.76 mg RE/g. The extract exhibited potent anti-tubercular activity with an MIC of 25 μg/mL.

Conclusion:
Citrus jambhiri fruit peel, rich in polyphenols and flavonoids, demonstrates promising anti-tubercular potential, supporting its use as a natural source for lead molecule development in TB therapy.