Current studies were performed to investigate the phytochemistry,
synergistic antibacterial, antioxidant, and hemolytic activities of
ethanolic and aqueous extracts of Azadirachta indica (EA and WA) and Cymbopogon citratus (EC and WC) leaves. Fourier transform infrared data verified the
existence of alcoholic, carboxylic, aldehydic, phenyl, and bromo moieties
in plant leaves. The ethanolic extracts (EA and EC) were significantly
richer in phenolics and flavonoids as compared to the aqueous extracts
(WA and WC). The ethanolic extract of C. citratus (EC) contained higher concentrations of caffeic acid (1.432 mg/g),
synapic acid (6.743 mg/g), and benzoic acid (7.431 mg/g) as compared
to all other extracts, whereas chlorogenic acid (0.311 mg/g) was present
only in the aqueous extract of A. indica (WA). Food preservative properties of C. citratus can be due to the presence of benzoic acid (7.431 mg/g). Gas
chromatography–mass spectrometry analysis demonstrated the
presence of 36 and 23 compounds in A. indica and C. citratus leaves, respectively.
Inductively coupled plasma analysis was used to determine the concentration
of 26 metals (Al, As, B, Ba, Ca, Cd, Co, Cr, Cu, Fe, K, Mg, Mn, Mo,
Na, Ni, Pb, Sb, Se, Si, Sn, Sr, V, Zn, Zr, Ti); the metal concentrations
were higher in aqueous extracts as compared to the ethanolic extracts.
The extracts were generally
richer in calcium (3000–7858 ppm), potassium (13662–53,750
ppm), and sodium (3181–8445 ppm) and hence can be used in food
supplements as a source of these metals. Antioxidant potential (DDPH
method) of C. citratus ethanolic extract
was the highest (74.50 ± 0.66%), whereas it was the lowest (32.22
± 0.28%) for the aqueous extract of A. indica. Synergistic inhibition of bacteria (Staphylococcus
aureus and Escherichia coli) was observed when the aqueous extracts of both the plants were
mixed together in certain ratios (v/v). The highest antibacterial
potential was exhibited by the pure extract of C. citratus, which was even higher than that of the standard drug (ciprofloxacin).
The plant extracts and their mixtures were more active against S. aureus as compared to E. coli. No toxic hemolytic effects were observed for the investigated extracts
indicating their safe medicinal uses for human beings.