Gas Chromatography-Mass Spectrometry (GC-MS) Metabolite Profiling of Citrus limon (L.) Osbeck Juice Extract Evaluated for its Antimicrobial Activity Against Streptococcus mutans

Abstract

Purpose The present study aimed to determine the antimicrobial nature of Citrus limon juice extract against Streptococcus mutans and to identify its metabolic profile by gas chromatography-mass spectrometry (GC-MS) technique. Materials and methods The cariogenic bacteria S. mutans were procured from Microbial Type Culture Collection and Gene Bank (MTCC), Chandigarh, India, and revived on brain heart infusion (BHI) agar. The C. limon (L.) Osbeck fruits were authenticated from the University of Trans-Disciplinary Health Sciences and Technology (TDU), Bengaluru, India. The antibacterial property of lyophilized lemon juice extract (LJE) dissolved in methanol was evaluated against S. mutans (MTCC 497) by the agar well diffusion assay. GC-MS technique was employed to identify the volatile metabolite profile of the methanolic LJE sample. The metabolite masses of the respective compounds were identified using the National Institute of Standards and Technology (NIST) library. Results The methanolic LJE sample concentration from 5 to 25 mg/ml did not demonstrate antimicrobial activity, while 30 to 100 mg/ml displayed antibacterial activity against S. mutans. Chlorohexidine (100 µg/ml) was used as the positive control, while methanol was used as the negative control. Significant antimicrobial metabolites were detected in the methanolic LJE sample by GC-MS analysis. Maleic anhydride, succinic anhydride, 6-Oxa-bicyclo[3.1.0] hexan-3-one, and 3-methyl-2,5-Furandione were the key metabolites identified in the methanolic LJE sample. Conclusion The present study reports that C. limon is a potential candidate for the pharmaceutical industry as it possesses bioactive compounds demonstrating therapeutic properties. Further investigations are warranted to determine the individual and synergetic effects of identified metabolites in the methanolic LJE sample for its antimicrobial property. Special attention needs to be focussed on translational research for the development of anti-caries products from C. limon.

Keywords: citrus limon; gc-ms; lemon juice; streptococcus mutans; dental caries.

Figure 1. Antimicrobial activity representing the zone of inhibition of lyophilized lemon juice methanolic extract at different concentrations against S. mutans. (A) No. 1 – 5 represents the concentrations from 5 – 25 mg/ml, (B) No. 6 – 10 represents the concentrations from 30 – 50 mg/ml, (C) No. 11 – 15 represents the concentrations from 55 – 75 mg/ml, (D) No. 16 – 20 represents the concentrations from 80 – 100 mg/ml, and (NC) is Negative control.

Figure 2. Gas Chromatography-Mass Spectrometry chromatogram of lyophilized lemon juice methanolic extract