Anti-cariogenic activities of crude and essential oil extracts from selected boswellia and commiphora (burseraceae) species

Abstract

Boswellia and Commiphara species are highly important aromatic plants belonging to the Burseraceae family. In the present study, three different species of these plants, Boswellia frereana (BF), Boswellia carterii (BC), and Commiphora myrrha (CM), were screened for their anti microbial activities. This research investigate the antibacterial activities of the crude extracts and essential oils obtained from the oleo gum resin against the cariogenic bacteria Streptococcus mutans (S. mutans), and Lactobacillus sp (L. sp.). Two different methods were used to extract bioactive compounds of the plant exudates: Organic solvent extraction was performed with Acetone, Methanol, and Hexane to produce crude extract while hydro distillation was used for essential oil extraction. The BF methanol extract exhibited the highest antimicrobial activity among the crude extracts with (10mm) inhibition zone for the two bacteria, followed by methanolic extract of CM (8mm) inhibition for S.mutans and (6mm) for L. sp respectively. However, BF essential oil displayed the best inhibition zone (16mm), where the other two essential oils (CM and BC) inhibition varied between 6mm and 2mm respectively. The BF and CM essential oils exhibited equal MIC (12.5μl/ml) and MBC (25μl/ml) on both bacteria species, while B. carterii essential oil gave two fold of these numbers (MIC 25μl/ml and MBC 50μl/ml) on S. mutans, but in the case of Lactobacillus sp it agreed with the other two essential oils. In organic solvents, the highest yield of crude extracts were 90% for BF and 80% for BC, yield of 10% was recorded on CM when hexane is used. Methanol extract of BF and BC were 65% and 68% while CM highest yield obtained on methanol was 30%. Acetone extracted 78% of BF, 60% of BC, and 22% of CM. Through hydro-distillation process, 8% of BF, 6% of CM, and 5% of BC essential oil was recovered. The hydro-distillation process was optimized in order to get the highest yield of BF essential oil. Following process optimization by FCCCD, with 13 runs of experiment, the highest BF essential oil production was achieved at 8.5%, using 10% solid/solvent ratio, and 3.5hours of distillation time, which slightly higher than the standard yield. Finally characterization of essential oil by Gas chromatography Mass spectrometry (GC-MS) revealed about 62 compounds present in the BF essential oil. The major chemical compounds in this oil are listed in Apendix F, where the β-Thujene, o-Cymene, and β-Phellandrene were found to be major components of the Boswellia frereana essential oil with estimation of 58.3%, 7.3% and 4.7% respectively. In the case of BC essential oil nearly 90 compounds were identified. However, some compounds exhibited significant quantities in the essential oil, where α-Pinene (44.82%), Sabinene (8.94%), D-Limonene (7.1%), o-Cymene (1.37%), Cyclohexene, 4-methyl-1-(1-methylethyl)- (4.26%), Neoisolongifolene (6.9%), and Acetic acid, octyl ester (4.43%) represent the major constituents of the oil (77.82%). Whereas, C. myrrha analysis revealed more than 100 different compounds mostly trace elements but, the most abundant compounds were; (1) d-α-Pinene at 3.74% (2) isofuranogermacrene at 33.5% (3) β-Elemene at 5.66% (4) Germacrene D 2.11% (5) α-Selinene 2.03%. These five compounds comprise nearly 50% of the essential oil chemical constituents. At the end of the study the B. frereana essential oil was selected as the best of all extracts for its high antibacterial activity and optimum yield of essential oil, compared to the other two oleo gum resins.