Part IV Natural antibioticals

Neem Tree

Neem oil and Neem leaf extract

[INCI: Melia azadirachta]

The neem tree is traditionally labelled The Village Pharmacy because of its multifaceted healing properties. These range from immunomodulatory and anti-inflammatory effects to antimicrobial and pesticidal attributes. The leaves and seeds of neem yield limonoids with wide biological applications. These have antibacterial, antiviral, insect repellant, anti-protozoal and anti-helmenthic properties.

The seed oil at a concentration of 0.3% on agar plates was active against Stahylococcus aureus and at 0.4% was active against Salmonella typhosa. The seed oil at a concentration of 3% on agar plates was active against E. coli and Proteus species. A concentration of 6.0% was active against Klebsiella pneumoniae. Methanol and butyl-methyl-ether extracts showed antifungal activity against the strains of fungi including Epidermaphyton floccosum, Microsporum canis, Microsporum gypseum, Trichophyton concentricum, Trichophyton entagrophytes, Trichophyton rubrum and Trichophyton violaceum.

A recent study determined the efficacy of a muco-adhesive dental gel containing Azadirachta indica leaf extract (25mg/g) using commercially available chlorhexidine gluconate (0.2% w/w) mouthwash as a positive control. The results of the study suggested that the dental gel containing neem extract significantly reduced plaque index and bacterial count as compared to the control group.

Green tea fields

Green tea extract

[INCI: Camellia sinensis leaf extract]

The catechins in green tea were found to inhibit Staphylococci and Yersinia entero-colitica. Green tea extracts may make strains of drug resistant bacteria more sensitive to penicillin. In vitro studies on Staphylococcus aureus revealed that the addition of green tea extract induced a reversal of penicillin resistance. It was found that epicatechin gallate markedly lowered the minimum inhibitory concentration (MIC) of oxacillin and other beta-lactams. Extracts of green tea were found strongly to inhibit Escherichia coli, Streptococcus salivarius and Streptococcus mutans, micro-organisms found in the saliva and teeth of people suffering from dental caries. Green tea in combination with the synthetic anti-oxidant butylated hydroxyanisole (BHA) reduced the hydrophobicity of S. mutans and greatly inhibited (p<0.001) the formation of hyphae in Candida albicans. The increased antimicrobial activity of green tea is related to an impairment of the barrier function in micro-organisms and a depletion of thiol groups.