Formulation and in vitro antibacterial screening of a bi-herbal syrup against some selected respiratory tract pathogens

Abstract

Introduction: Respiratory tract infection remains one of the most significant cause of death and hospital visit globally, with high burden in developing countries. The aim of the study was to formulate and carry out in vitro antibacterial screening of bi-herbal syrup against some selected respiratory tract pathogens. Methods: 75% ethanol extracts of Citrus aurantifolia (CA) whole fruits and Garcinia kola (GK) seeds were made by cold maceration. Antibacterial activity and optimum minimum bactericidal concentrations (OMBC) of each extract (singly and combined) were determined using agar well diffusion and pour plate methods respectively. Formulations of the bi-herbal syrup were compounded by agitation without heat application method and re-evaluated for antibacterial activities. Results: The percentage yield were 12.68 and 7.09 for CA and GK respectively. The extracts were tested against Streptococcus pyogene, Streptococcus pneumoniae and Staphylococcus aureus. The MIC of the extracts varied from one pathogen to another. Clinical Staphylococcus aureus was highly resistant to GK, to the extent that the MIC value was indeterminate. However, CA exhibited more potent antibacterial activity with MBC ranging from 4.76- 9.53mg/mL than GK (MBC: 28.60 to 34.76 mg/mL). An optimal minimum bactericidal concentration of 9.523mg/mL (0.9523 % w/v) of Citrus aurantifolia whole fruits extract exhibited a total clearance of all the isolates tested, while 34.76 mg/mL (3.476% w/v) of Garcinia kola seeds extract did the same .When tested singly, the average zone of inhibition of the bacteria showed that the OMBC of CA tends to increase in diameter with increase in percentage concentration against the isolates while that of GK varied. The highest efficacy of the combined OMBC was at 85% ≡ 37.64mg/mg. At this concentration, a total kill on all the isolates tested was observed. An assessment of all the formulations with this same concentration and varying excipients concentration, showed that the average zone of inhibitions against all the isolates were higher than the standards used as positive controls at P-value of 0.05. Conclusion: A combination of Citrus aurantifolia and Garicia kola extracts have shown in vitro antibacterial activities and therapeutic potential effects in vivo which was retained when the extracts were formulated into a bi-herbal syrup