Antimicrobial properties of some plant essential oils against two human pathogens

Introduction

Modern civilization has got health conscious about the problems face by them. Athlete’s foot, or Tinea pedis and Dandruff are among the most common infection of the skin and feet caused by a variety of dermatophytes. These include conditions that affect otherwise healthy individuals. These pathogens most often affect the space between the toes leaves the person uncomfortable. Trichophyton rubrum is a typical dermatophyte that cause noninflammatory chronic infections that are easily transmitted that the infection is characterized by skin fissures or scales that can be red and itchy. Dandruff is among the serious problems faced by the modern youth. Use of synthetic chemicals has caused huge financial losses and rendered the pathogens resistant.

The worldwide problem of infectious diseases has appeared in recent years, and antimicrobial agents are crucial in reducing disease emergence. Essential oils could serve as a promising tool as a natural drug in fighting the problem with these fungi. Essential oils from medicinal and aromatic plants have been explored for their complex volatile compounds, synthesized naturally in different plant parts during the process of secondary metabolism. These naturally occurring compounds have got different types of aldehydes, phenolics, terpenes, and other antimicrobial compounds which help in managing different fungal infections. The antipathogenic activity of essential oils is believed to be due to presence of strong volatile reactive functional groups. Essential oils have been tried in the field of biomedicine against several bacterial, fungal and viral pathogens. Since ancient times, folk medicine and agro-food science have benefited from the use of plant derivatives, such as essential oils, to combat different diseases, as well as to preserve food.

In nature, essential oils play a fundamental role in protecting the plants and animals from biotic and abiotic attacks to which it may be subjected. Essential oils have been explored for their bioactive compounds by researchers. The main aim of this study is to investigate the positive potential of essential oils as anti-dermatophytes espatially Candida albicans and Trichophyton rubrum.

Essential Oils

Essential oils are natural, volatile, complex plant compounds, oily or lipid-like both polar and non-polar in nature and frequently characterized by a strong fragrance.1, 2 They are stored in specialized plant cells, usually oil cells or ducts, resin ducts, glands or trichomes (glandular hairs).3, 4 and may be extracted from the leaves, flowers, buds, seeds, fruits, roots, wood or bark of plants. Essential oils make up only a small proportion of the wet weight of plant material, usually approximately 1% or less.3, 5 The presence, yield and composition of essential oils may be influenced by many factors, including climate, plant nutrition and stress.6

There is an increasing demand to reduce the use of chemicals as antimicrobial agents by providing alternate solution and remedy to combat various infections due to various notorious and aggressive dermatophytes. Over the passage of time microbial resistance against synthetic antimicrobials is the most concern topic. In this direction the hydo-alcoholic extracts or essential oils play a positive role to combat such issues. These substances are the treasures of many versatile molecules that act as broad spectrum antibiotics.

Swiss reformer of medicine, Paracelsus von Hohenheim coined the term “Essential Oil” (EO) in 16th century, well-known for their antiseptic and medicinal properties (analgesic, sedative, anti-inflammatory, spasmolytic, local anesthetic, anti-carcinogenic), they are also used in embalmment,and, due to their antimicrobial and antioxidant activity, as natural additives in foods and food products.7, 8

Antipathogenic Effects of Essential Oils

Essential oils and their constituents have got a wide range of antipathogenic effects. The essentials oils extracts from many plants such as Clove, Luclaptus, lavander, Oregano, Rosemary, and Ttree tea have shown considerable antifungal activity against a wide range of fungal pathogens.9 Arora and Kaur10 worked on the antimicrobial activity of essential oils extracted from spices against fungal pathogens and found that garlic and clove extracts limit the growth of several fungal pathogens including several Candida species, Rhodotorula rubra,Saccharomyces cervisiaei and Trignoposis variablis. Similar results were observed by Grohs and Kunz 11 whom investigated mixtures of ground spices and analysed their efficacy against the C. lipolytica. Essential oils extracted from onion and garlic plants contain isothiocyanate which have been found very effective against several fungal infections,12

Isothiocyanates have been found effective against Botrytis, Fusarium, Penicillium, and Cladosporium species by inactivating the extracellular enzymes through oxidative cleavage of disulfide bonds. 13 observed the antifungal activity of essential oils and their derivatives on the cell viability, mycelium growth, and mycotoxin-producing ability of molds.14

Figure 1

Antifungal activity of essential oils against Candida albicans and Trichophyton

Materials and Methods

Commercially available essential oils of clove, geranium, oregano, tea tree, rosemary, eucalyptus, and lavender used in this research were purchased from a local distributor in New Delhi India. According to certification, essential oils from plants were pure in form.

A total of two fungal human pathogenic strains were used in this study. They were identified by conventional fungal stains.

The poison food method of antifungal activity was used for antimicrobial testing of essential oils.

Antifungal assessment of the isolated essential oils was conducted using a mycelial radial growth inhibition technique against Candida albicans and Trichophyton. The oils were diluted with acetone and added to sterilized PDA medium before pouring in 9-cm Petri dishes. The oils were tested at concentrations @ 1000 mg L^-1. Incubation of inoculated fungi was conducted for 8 days at a temperature of 27 ◦C, in PDA plates.

The inoculum of mycelial culture of fungi, taken from 8-day-old cultures, was transferred aseptically to the Petri plates. The plates were incubated at 27⁰C in the dark. Three replicates were setup with a control. Colony growth was measured after the fungal growth in the control as well as in the treatments. Inhibition percentage of mycelial growth was calculated as follows:

Mycelial growth inhibition (%) = [(DC- DT)/DC]*100 Where DC and DT are average diameters of fungal growth of control and treatment, respectively.4

Based on the results obtained, Table 1. As depicted in the Figure 1 it can be concluded that clove essential oil, geranium essential oil, lavender essential oil are the most active inhibitor against Candida albicans and Trichophyton, while as. rosemary,oreganum and euclaptus essential oils were less effective against the above fungi. Mineral oil as control also doesn’t show any antifungal activity against Candida albicans and Trichophyton.

Result and Discusion

Source of Funding

None.

Conflict of Interest

None.