Antibacterial Properties of Alkaloid Extracts from Callistemon citrinus and Vernonia adoensis against Staphylococcus aureus and Pseudomonas aeruginosa

Abstract

The development of new antibiotics from new chemical entities is becoming more and more expensive, time-consuming, and compounded by emerging strains that are drug resistant. Alkaloids are plant secondary metabolites which have been shown to have potent pharmacological activities. The effect of alkaloids from Callistemon citrinus and Vernonia adoensis leaves on bacterial growth and efflux pump activity was evaluated on Staphylococcus aureus and Pseudomonas aeruginosa. At a concentration of 1.67 mg/mL, the alkaloids inhibited bacterial growth with comparable effects to ampicillin, a standard antibiotic. The alkaloids from C. citrinus were the most potent against S. aureus with an MIC of 0.0025 mg/mL and MBC of 0.835 mg/mL. It was shown that effects on P. aeruginosa by both plant alkaloids were bacteriostatic. P. aeruginosa was most susceptible to drug efflux pump inhibition by C. citrinus alkaloids which caused an accumulation of Rhodamine 6G of 121% compared to the control. Thus, C. citrinus alkaloids showed antibacterial activity as well as inhibiting ATP-dependent transport of compounds across the cell membrane. These alkaloids may serve as potential courses of compounds that can act as lead compounds for the development of plant-based antibacterials and/or their adjunct compounds.

Antimicrobial and Physicochemical Evaluation of <i>Luffa acutangular</i> Leaf Extracts

“…In this study, the presence of alkaloids, phenolic acid, saponins, tannins, terpenoids and triterpenoids (table 1) suggests that the plant possess a unique antimicrobial range as these individual compounds exert action that thwarts the growth or development of disease causing pathogens [23]. Recent studies have shown that alkaloids, obtained from different plant extracts like Callistemon citrinus and Vernonia adoensis successfully diminished the growth of Staphylococcus aureus when compared to β-lactam antibiotics [24]. Bioactive compounds like tannins has also been studied and found to be active against Staphylococcus aureus alongside a host of bacterial pathogens linked with a variety of infections [25][26].…”

Phytochemical Screening and <i>in Vitro</i> Antimicrobial Activity of <i>Waltheria Indica Linn</i> Leaf Extracts

“…The presence of alkaloids alone is highly suggestive of a broad antimicrobial spectrum as alkaloids are reportedly extensively used as pharmaceuticals, psycho-stimulants, narcotics and poisons due to their renowned biologic activities [48]. The activity of alkaloids have been investigated in plants like Callistemon citrinus and Vernonia adoensis whereby at concentrations of 1.7mg/ml, it inhibited the growth of Staphylococcus aureus with comparable effects to ampicillin [49]. Other possibilities include the synergies between phenolic acids and tannins, both of which have been studied and found to be active against Staphylococcus aureus alongside a host of bacterial pathogens linked with respiratory infections [50].…”

Antioxidant and antimicrobial activity and potential of heather (Erica spp.) extracts in the control of Listeria monocytogenes

“…Despite the availability of a wide range of antibiotics, microorganisms are constantly developing mechanisms of resistance to these agents (Mabhiza et al, 2016). Therefore, the increased microbial resistance leads to the development of new antimicrobial agents, such as molecules present in natural sources (Sassi et al, 2007).…”