The effects of plant extracts on bacteria have been studied by a very large number of workers, in different parts of the world. The diverse species of plants used for this type of study, the different types of bacterial models and the large number of workers from different labs, have all contributed models and the large number of workers from different labs, have all contributed to a lack of cogency and order. Comparability between studies is minimal.

It is necessary that plants with possible antimicrobial activity should be tested against an appropriate microbial model to confirm the activity and to understand the parameters associated with that activity. In order to evaluate the efficacy of species indicated against a particular disorder, it is apt to test only those pathogens responsible for that disorder. For example, if we are at finding species of plants with antimicrobial activity in gastro-intestinal disorders, tests should be conducted against gastro-intestinal pathogens. Such correlated studies are not common.

Dr Assumpta Sharon has isolated gastro-intestinal pathogens from patients in St. John’s Medical College Hospital, Bangalore, and studied the effects of species used in gastro-intestinal disorders against them, in order to verify the validity of the claims in traditional literature. As these extensive data (Sharon, 1994) cannot be presented here, a summary of the results is given in Table 1. Quite a number of them proved to be either bacteriostatic or bactericidal. Most of the plant extracts used contained lectins. In separate tests she found that some extracts agglutinate the pathogenic bacteria, which certainly affects their growth. More importantly, some extracts did not agglutinate bacteria, but have inhibited their growth (Sharon, 1994). Consequently, cell agglutination and inhibition of growth are independent phenomena.

The most interesting among the extracts tested was that of the fruit rind of pomegranate (Punica granatum), which is a waste product. This nontoxic extract was very effective against a broad range of intestinal pathogens, more particularly the cholera bacterium. Also used in traditional medicine, pomegranate holds a good promise of becoming one of the most potent medicines against gastro-intestinal infections (Sharon, 1994).

It is necessary to assess the bacteriostatic efects of plants extracts against standard antibiotics, in order to obtain a scientific and comparative basis to excercise choices. The results of such a study on gastro-intestinal pahogens are given in Appendix 37. Obviously, several of the species of plants here are very potent antibacterials. Their use in traditional medicine is quite justified. The effects of pomegranate fruit rind extracts also compare very favourably with standard antibiotics.

Dr Shubharani has conducted a similar study employing extracts of several species of plants used in dental care against oral pathogens and found that some of them function as as bacteriostatic and/or bactericidal agents (Shubharani, 1995). On a comparison of the results obtained by Fadula (1975), on west African species, the data discussed by Oliver-Bever (1986), and the results of Sharon (1994) and Shubharani (1995), the following species, all of which are in use in traditional medicine, appear to be effective in the control of oral bacteria, and can be used as tooth brushes, chewing sticks, tooth powders, and in medication:

Anacardium occidentale, Artocarpus heterophyllus, Azadirachta indica, Cocos nucifera, Emblica officinalis, Jatropha gossypifolia, Mnagifera indica, Moringa oleifera, Psidium guajava, and Punica granatum,

TABLE 1

AGGLUTINATION AND INHIBITION OF GASTRO-INTESTINAL

PATHOGENIC BACTERIA BY PLANT EXTRACTS

(Data gathered by Dr Assumpta Sharon)

	Pathogen	Number of Samples Tested	Number of Samples Positive
1	Candida albicans	101	56
2	Escherichia coli	102	32
3	Proteus mirabilis	16	8
4	Pseudomonas aeruginosa	77	24
5	Salmonella typhii	101	37
6	Shigella boydii	5	3
7	Shigella dysenteriae	3	2
8	Shigella flexneri	112	19
9	Shigella sonnei	95	29
10	Staphylococcus aureus	117	42
11	Vibrio cholerae	119	36

The pathogens were extracted from patients in hospital

Plant extracts were made in PBS 1:10 w/v

REFERENCES

Fadula, S.A. 1975. The antibacterial properties of the buffer extracts of chewing sticks used in Nigeria. Planta Medica, 27: 122-126.

Oliver-Bever, B.E.P. 1986. Medicinal plants of tropical west Africa. Cambridge Univ. Press, Cambridge.