Antibacterial Effect of Pepper and Chilli against Staphylococcus Aureus: A Comparative Study

Introduction

Antimicrobial properties of the phytochemicals or natural therapeutics were notable alternative to modern antibiotic drugs. Recent clinical report suggests that most of the microorganisms were developing resistance to many commonly used antibiotics because of the improper protocol of antibiotics prescriptions [1]. Hence scientific community is showing interest in the use of photochemical and nutritional supplements as agents to cure many diseases. Plant extracts and secondary metabolites possess antimicrobial, antifungal or antiviral activities. Various plant products regularly used for their therapeutic potential, and plant products that form the part of the food or as dietary components, have been receiving considerable attention. Though much is known about the chemistry and antimicrobial action of several phytochemicals, very few reports are available on the possible use of nutritional supplements in this regard.

Piper nigrum (Black pepper/ Pepper) commonly known as the King of spices due to its pungent quality [2] is a member of family Piperaceae [3, 4, 5]. Dried ground pepper has been used since antiquity both for its flavour and as a traditional medicine. Black pepper is the world's most traded spice, and is one of the most common spices added to cuisines around the world. Its spiciness is due to the chemical piperine. It is ubiquitous in the modern world as a seasoning and is often paired with salt. Black pepper can be used for different purposes such as human dietaries, as medicine, as preservatives, as biocontrol agents [2, 6, 7]. This plant and its active component piperine can stimulate the digestive enzymes of pancreas and intestine and also increases biliary bile acid and secretion when administrated orally [8]. Piperine prevents and minimize diarrhea produced by various oils and chemicals and also reduce intestinal fluid in mouse intestine [9].

P. nigrum has anti- inflammatory activity, thermogenic action, growth regulatory activity, anti-thyroid activity and chemopreventive [10]. Secondary metabolites from P. nigrum are reported to play defensive role against infection by microbes, insects and animals [4]. Medicinally black pepper can be used for digestive disorders like large intestine toxins, different gastric problems, diarrhea, and indigestion and also can be used against respiratory disorders including fever, cold, asthma [11].

Capsicum annum var glabriusculum is a domesticated species of plant genus in the family solanaceae [12]. Foods containing peppers, especially chili peppers, often have a strong aftertaste which is due to the presence of capsinoids in peppers [13]. They are rich sources of vitamin C (ascorbic acid) and vitamin A. In addition to the use of capsicum fruits as a food additive, in traditional medicine, it has been used for the treatment of parasitic infections, rheumatism, and wound healing [14] and also utilized as an antiseptic, counterirritant, appetite stimulator [15], antioxidant and immunomodulator [16]. The medicinal effects of chilies are related to different constituents such as capsaicin, fixed oil, thiamine, protein and ascorbic acid [15].

P. nigrum and Capsicum fruitscence are commonly used spices in most of the food preparations in daily life. There is a common belief among different community of people regarding the magical effect of these spices in preventing or curing diseases. But a clear scientific backup for these ideas are lacking and hence we check their antimicrobial activity against a common pathogenic bacteria Staphylococcus aureus. Staphylococcus aureus (S. aureus) belongs to the family micrococcaceae family and causes a wide range of infections from a variety of skin, wound and deep tissue infections to more life-threatening conditions such as pneumonia, endocarditis, septic arthritis and septicemia. This bacterium is also one of the most common species in nosocomial infections. In addition, S. aureus may also cause food poisoning, scalded-skin syndrome and toxic shock syndrome, through production of different toxins. Since S. aureus is an opportunistic pathogen_,_ we selected this strain for testing the antimicrobial property of the two spices which forms our regular dietary supplements.

The present investigation is aimed to identify the broad spectrum antimicrobial activity of P. nigrum and Capsicum extracts against S. aureus. To achieve this goal, the bacterial strain was isolated from soil sample and characterised by various standardized protocols. This bacterium was used for studying the antimicrobial activity of P. nigrum and Capsicum by disk diffusion method. A systematic analysis like this is expected to give an idea about the antimicrobial effects and the relative efficiency among the two species selected for the study.

Materials and Methods

Eight soil samples were collected from different sites and locations of Thodupuzha, Kerala, India. Soil samples were collected at a depth of 0.75m from the surface. The samples collected were serially diluted and streak plated on nutrient agar for the purification and separation of colonies.

Discussion

Many plant derived molecules have shown a promising effect in therapeutics. Spices are recognised as source of natural antioxidants and thus play an important role in the chemo preservation of diseases and ageing. Among plants investigated to date, the enormous potential of Piper nigrum is reported. Here, we investigated the antimicrobial activity of acetone extract of Piper nigrum and Capsicum annum var.glabriusculum on Staphylococcus aureus. In the present study, the bacterial strain isolated from soil microfauna was identified on the basis of cultural, microscopic, morphological and16S rRNA genome sequencing data.

The result of our study showed the inhibitory effect of Capsicum annum var.glabriusculum on S. aureus as evident from a clear zone of inhibition of 1.700cm around the disc. Previous studies revealed that C. annuum var.glabriusculum have strong antimicrobial activity against Vibrio cholera, a gram negative Enterobacteriaceae [19]. The aqueous and isopropanol extracts of Capsicum species is found to be effective against Salmonella and Pseudomonas [20]. It is also reported that the aqueous extract from fresh Capsicum species showed varying degree of inhibition against Bacillus, Salmonella, Streptococcus and Clostridium spp [21]. Rose Koffi-Nevry, et al. [22] reported that flavanoids and other active components like capsaicin have potential antibacterial activity as it is major compound from Capsicum species. Based on previous studies we assumed that in the present study, the flavanoids or capsaicin might have contributed the anti-microbial activity of capsicum extract against S. aureus. Piper nigrum showed a prominent zone of inhibition of 2.05cm diameter by disk diffusion method against S. aureus. Previous studies reported the excellent inhibitory effect of acetone extract of black pepper on the growth of Gram positive bacteria [23]. Here, we found that P. nigrum can also show an effective inhibition of the growth of S. aureus too.

The present work also revealed that the effectiveness of P. nigrum against S. aureus was higher than that of the C.annuum var glabriusculum extract. From the study we can conclude that both P. nigrum and Capsicum annuum var glabriusculum extracts are effective against the growth of S. aureus with P. nigrum showing a significantly higher antimicrobial activity than Capsicum annuum var glabriusculum.

To conclude our results, we clearly observed and validated the inhibition of Staphylococcus aureus growth by both Piper nigrum and Capsicum annum var glabriusculum extracts invitro. Further analysis of the data by statistical tools showed the more potent effects of Piper nigrum than Capsicum annum var glabriusculum against Staphylococcus aureus. This can be considered as a first report on the comparative analysis of two commonly used spices in diet to address the question of overall health benefits which can be impacted by them. Further study in this direction will help in proving that the Queen of spices — black pepper — is not only a delicacy in Indian culinary but a health booster and prophylactic too.

Acknowledgement

The authors acknowledge Newman College, Thodupuzha for providing the infrastructural facilities to conduct the work. This work was supported by the grant from KSCSTE, Govt. of Kerala under SPYTiS-II programme to Dr. Anju T R & Neethu Gopal.