IN VITRO ANTIMICROBIAL ACTIVITY OF COMBINATIONS OF Callistemon citrinus AND Eriobotrya japonica AGAINST CARIOGENIC Streptococcus mutans
HEALY ONEN1, JUDITH SIFA KAVUO1, GERALD KUTOSI NAMBOKO1, SAMUEL BUKUSUBA1,
DERRICK HOPE2, JIMMY RONALD ANGUPALE1,3,*
1. Department of Pharmaceutical Sciences, Faculty of Medicine, Mbarara University of Science and
Technology, P.O Box 1410, Mbarara-Uganda
2. Microbiology Laboratory Epicentre Uganda, Mbarara University of Science and Technology Campus, P. O
Box 1596, Mbarara – Uganda.
3. Pharm- Biotechnology and Traditional Medicine Center (PHARMBIOTRAC), Mbarara University of Science
and Technology, P.O Box 1410, Mbarara-Uganda
Afr. J Pharm Res Dev; Volume 14(2): 195-203 ; 2022
ABSTRACT
Eriobotrya japonica (EJ) and Callistemon citrinus (CC) have been reported to separately have antimicrobial activities against Streptococcus mutans (the aetiological agent for dental caries), but their potential for beneficial synergistic, additive, or potentiative effects, when used in combinations has never been reported. The current study explored the possibility of in vitro antimicrobial interactions between EJ and CC ethanolic leaf extracts against the bacterium. The leaves of both plants (EJ and CC) were shade-dried and pulverized into a coarse powder. These were cold macerated using ethanol (60 %) for 24 h and phytochemical screening was conducted. Various combinations of the extracts (CC: CJ – 1:0, 3:1, 1:1, 1:3, and 0:1) were subjected to minimum inhibitory concentrations (MIC) and minimum bactericidal concentration (MBC) determinations against Streptococcus mutans. Ciprofloxacin and 2.5 % Dimethyl sulfoxide (DMSO) was used as the positive and negative controls respectively. Antimicrobial interactions between the two extracts were evaluated using Fractional Inhibitory and Bactericidal Concentration Indices (FICI and FBCI). The extraction method yielded 20.05 % and 15.45 % crude extracts of EJ and CC respectively. Both extracts demonstrated almost similar phytochemical profiles revealing the presence of flavonoids, saponins, and tannins, and the absence of alkaloids and volatile oils. The combination CC: EJ (1:0) having only CC exhibited the lowest MIC and MBC comparable to that of the standard drug at P <0.05. The FICI/FBCI values obtained for the combinations were between 1.5 and 3.917 indicating no antimicrobial interactions between the two plant extracts. Therefore, a combination of Calistermon citrinus and Erybotrya japonica hydro-ethanolic leaf extracts may not have any synergistic, additive, or potentiative in vitro antimicrobial activity against Streptococcus mutans. Instead, the Calistermon citrinus leaf extract is more efficacious against the cariogenic bacteria when used singly than its mixture with Erybotrya japonica leaves extract.
Email of correspondence:jangupale@must.ac.ug;
KEYWORDS:Antimicrobial; Streptococcus mutans; Callistemon citrinus; Eriobotrya japonica; Hydroethanolic;
interactions .