INTRODUCTION
The use of medicinal herbs and herbal medicines is an age-old tradition and the recent progress in modern therapeutics has stimulated the use of natural product worldwide for diverse ailments and diseases (Miraj, 2016) . Furthermore, the growing concerns of multi-drug resistant pathogens have paved way to the development and utilization of natural antimicrobials as an alternative mode of disease management (Priti et.al. 2014). Screening of natural medicinal plants is now being popular because many infectious diseases are known to have been treated with herbal remedies throughout the history of mankind (Ozcan et al., 2010). Many naturally occurring compounds found in dietary and medicinal plants, herbs and fruit extracts have been shown to possess antimicrobial activity.
One of the medicinal plants and herbs that said to be possessed with antimicrobial or antibacterial chemical components is the Oregano (Organum Vulgare). Origanum vulgare L., commonly known as oregano or wild marjoram, is a well-known flavouring for many international dishes and has antioxidant applications in human health (Dorofeev et al., 1989; Deighton et al., 1993 cited in Kozlowska et. al. 2015 ). Antimicrobial action is reported for O. vulgare extracts, which contained phenolcarboxylic acids (cinamic, caffeic, p-hydroxybenzoic, syringic, protocatechuic, vanillic acid) as presumably active substances (Mirovich et al., 1989).
According to Ozcan et. al., numerous studies have been published on the antimicrobial activities of plant compounds against many different types of microorganisms, including foodborne pathogens.
Moreover oregano belongs to the family of Lamiaceae. Many studies showed that herbs from the Lamiaceae family have a potent antioxidant and antibacterial activities, mostly due to the quantity and quality of phenolic compounds present in them among these, eugenol, carvacrol and thymol which are the major components of essential oils are primarily responsible for their bactericidal/bacteriostatic properties (Kozlowska et. al. 2015).
However, it was also observed, that the antimicrobial effect of plant extracts varies from one herb to another in different regions of the world. This may be due to many factors such as: the effect of climate, soil composition and many variables (Kozlowska et. al. 2015). . In line with the gap of this study, the goal of this present study is to assess the antibacterial activity of the oregano that can be seen in Iligan City considering the different factors that can cause bias. The main purpose of this study was to verify he chemical composition and characterize the antibacterial activities of herbs extract against Gram-positive and Gram-negative bacteria.
METHODS
Materials:
The aerial parts of oregano (Origanum vulgareL.) were collected from Iligan City, Philippines.
Essential oil:
The essential oil used for the study was Oregano oil were obtained from Iligan City, Philippines.
Recovery of the essential oils:
Dried aerial parts of the plant (200 g) were ground and submitted to hydro-distillation for 4 h using a Clevenger-type apparatus and the oils obtained were dried over anhydrous sodium sulfate. The essential oils were light dark- yellow.
Microbial cultures used:
The test organisms selected for the study were a series of Gram positive and negative bacterial pathogens.
Assessment of Antimicrobial activity:
The antibacterial activity of Oregano oil was determined against selected bacterial pathogens by agar cup double dilution method. On the basis of available literature, four diluents namely Olive oil, Ethanol, DMSO (dimethylsulfoxide) and DMSO with Tween 80 were selected for study. Olive oil exhibited no zone of inhibition against the test organisms and hence was the diluent of choice; however with olive oil as the diluent, the antibacterial activity of Oregano was found to be less as compared to ethanol. Hence ethanol was selected as the diluent of choice. For determination of MIC, double dilutions of Oregano oil were performed using ethanol as the diluent on MH (Mueller Hinton) agar plates. Pure ethanol served as control.
Antimicrobial screening
Antibacterial activity of herbs extracts was examined by the disc-diffusion method and the MIC
method under standard conditions using MuellerHinton II agar medium (Beckton Dickinson) according to the guidelines established by the CLSI (11, 12). For the disc-diffusion assay, the solutions of tested herbs extracts were prepared in methanol (70%) or ethanol (70%), respectively. Sterile filter paper discs (9 mm diameter, Whatman No. 3 chro matographic paper) were dripped with tested herb extract solutions to load 2 mg of a given extracts per disc, and were placed on the agar plates uniformly inoculated with the test microorganisms.
The paper discs with 70% ethanol and 70% methanol were used as negative control. Nitrofurantoin was used as a positive control (300 µg/disc). The diameter of the clear zone surrounding the disc after 18 h incubation at 35 ± 2.5 OC was the measure of antimicrobial activity of a given extracts. For MIC (minimum inhibitory concentration) determination, the solutions of the tested spice extracts were prepared in dimethyl sulfoxide (DMSO), and were added to liquid solution of the agar medium to form two-fold serial dilutions covering the range from 31.3 to 2000 mg/L. The plate of agar medium with DMSO was used as a control of the bacterial growth in the presence of the solvent, the so-called negative control.
Next, solidified agar plates were inoculated using 2 µL aliquotos. The final inoculum of all studied organisms was 104 colony forming units (CFU)/mL, except the final inoculum of E. faecalis ATCC 29212 which was 105 CFU/mL.
Statistical analysis
Data were analyzed using analysis of variance (ANOVA) with post-hoc Tukeyís HSD at the confidence level α= 0.05 (Statgraphics Centurion XV software, Statpoint Inc., Warrenton, Virginia, USA).
REFERENCES:
Baricevic, D. et al., (2012). The Biological/pharmacological activity of the Origanum Genus. Taylor and Franciss, (8); 179-213.
Kozlowska, M. et al., (2015). Chemical Composition and Antibacterial Activity of Some Medicinal Plants From Lamiaceae Family. Polish Paharmaceutical Society. Vol. 72 (4); 757 – 767.
Miraj, S. (2016). Antioxidant, Anticancer, Antimicrobial potential of Oreganum Vulgare. Scholars Research Library, Vol. 8 (13); 89-97.
Mirovich, V.M., Peshkova, V.A., Shatokhina, R.K. and Fedoseev, A.P. (1989) Phenolcarboxylic acids of Origanum vulgare. Khimiya Prirodnykh Soedinenii25(6), 850–851.
Ozcan, M. et.al., (2010). The Antibacterial Activity of Essential Oil of Oregano (Oreganum Vulgare L.). Journal of Food, Agriculture and Environment, Vol. 8 (2); 272-274.
Priti,U., Vidhi, M. (2014). Antibacterial Activity of Origanum Vulgare (Oregano) Oil. BIONANO Frontier, Vol.7 (2): 47 – 49.
Disclaimer: This paper analysis is from my roommate Mr. Christian metillo, with his consent and permission to post this.
