Antimicrobial Activity of Plants Belong to Solanaceae Family

Berberine
Berberine is an alkaloid found in a herb called barberry (Berberis vulgaris) and related plants as well as in goldenseal, oregon grape root and Chinese goldthread. This herb has long been used in chinese and ayurvedic medicine. Berberine has significant anti-fungal activity and is also effective against some kinds of bacteria. As with all previously covered anti-fungal's, berberine is reported to spare beneficial organisms such as lactobacilli species. An added benefit for some people is its anti-diarrheal action. Research has shown that berberine can effectively prevent candida species from producing an enzyme called lipase which they use to help them colonize[3]. Berberine has also been widely shown to have a powerful directly anti-fungal action [4,5] Cost of treatment with berberine is roughly equivalent to that of the fatty acids.

Oregano
Most people will be familiar with oregano as the strong smelling herb commonly used as a seasoning in Italian food. This is usually Oregano marjoram rather than Oregano vulgare that we're interested in here. Oregano vulgare contains a variety of substances that make it an effective anti-fungal. In a study assessing its action against Candida albicans, carvacrol, a major phenolic constituent of the oil, was found to inhibit candida to a greater extent than caprylic acid. It is also highly effective against many bacteria with studies published in the most prestigious medical journals showing it is as effective as many antibiotic drugs. Usually supplied in oil form, oregano treatment will cost around $25 per month. It is very potent so only a few drops in a glass of water are needed at a time. Higher dosages would be likely to cause irritation of the mucous membranes. 

Garlic
Garlic (Allium sativum) contains a large number of sulphur containing compounds that exhibit potent anti-fungal properties. Among the most studied are allicin, alliin, alliinase and S-allylcysteine. Some studies have found garlic to be at least as effective as nystatin at killing Candida albicans. A point that should not be overlooked is that because of the many different compounds with anti-fungal properties in garlic, yeast and fungi are unlikely to become resistant to it. Garlic also has many other beneficial properties particularly for the cardiovascular system. It has been shown to lower levels of LDL cholesterol and act as an anti-coagulant, lowering blood pressure as a result. Like barberry, garlic has a long history of medicinal use, reportedly dating back as far as 3000 years. For treating intestinal yeast infections garlic is available in a number of different forms including, odorless capsules, liquid extract and tablets. However, a study at the National Institutes of Health found that fresh garlic was significantly more potent against Candida albicans. It also found that the fresh garlic could be a suitable alternative to drugs for serious systemic infections in patients with severe immune suppression. Therefore adding garlic to food (raw) or crushing and swallowing raw cloves if you can tolerate it, is a cheap and powerful anti-fungal treatment.

Colloidal Silver
A colloid is defined as very small particles of one substance suspended (not dissolved) in another. Colloidal silver is a suspension of silver particles in water. Silver is a well known anti-microbial, it is commonly used in items such as water filters to kill any microbe that may be in the water, including bacteria, fungi, worms and protozoa. Colloidal silver is said to be effective against up to 650 pathogens including, of most interest to us here, yeast and fungi species including Candida. It works by denaturing the enzyme involved with supplying the organism with oxygen. Chances of resistance to this process are by all accounts, very low. It was used widely to treat infection before the development of antibiotic drugs. It is now classified as a pre-1938 drug by the FDA which means that it is available without prescription. The number of companies offering colloidal silver as an alternative to antibiotic medications is increasing daily. The renewed interest can be explained by the increase in chronic infections and the fact that many microbes are becoming resistant to the commonly used drug treatments. The dosage of colloidal silver needed to treat yeast overgrowth will vary between products because they may have slightly different concentrations. Prices are similar to the other natural products discussed at about $30 for an 8oz bottle.

Cellulase
This is a relatively new treatment approach for intestinal yeast infections. The cell wall of common intestinal yeast such as Candida species have been found to be made mainly from cellulose. Cellulase is the enzyme that breaks down cellulose and hence, when significant concentrations come into contact with yeast cells the cell wall is irreparably damaged and the organism dies. It's claimed that using this mode of action, the yeast do not release a flood of toxins when they die as occurs with most other anti-fungal agents so that the sufferer does not experience the usual die-off symptoms to any significant degree. The yeast should be unable to develop resistance to cellulase products as they lack the ability to modify their cell wall. As cellulase products have only been around for a few years reports of their effectiveness in practice is limited but they offer a promising alternative to more established treatments. Prices again, are in a similar range to all the natural anti-fungal's.

PlantTannins
Tannins are natural substances found in a number of plants such as Black Walnut and a vast array of plants used in traditional eastern medicine. Tannins are what give red wines such as merlots and cabernets their sharp, biting taste. They are also found in the bark of trees that are particularly resistant to fungus such as the redwood tree. They have been demonstarted to have a powerful anti-fungal and astringent action in a multitude of clinical studies[6,7,8]. Tannins are one of a number of natural substances tested against pathogens found in stool samples by functional medicine labs. More information can be found on these tests here. Tannins are available in a number of froms to treat intestinal yeast overgrowth. As previously mentioned they are the active anti-fungal ingredient in many traditional eastern herbal preperations. Black walnut has a very high tannin content and is commonly used to treat infections with Candida sp, parasites and worms. It is widely available from health stores and nutritional supplement suppliers. Tannins are also available in an isolated and concentrated form. Treatment with plant tannins is comparable in cost to most natural anti-fungal agents, being in the region of $15-$30 per month

Historic Use of Plants as Antimicrobials
Historically, plants have provided a source of inspiration for novel drug compounds, as plant derived medicines have made large contributions to human health and well-being. Their role is two fold in the development of new drugs: (1) they may become the base for the development of a medicine, a natural blueprint for the development of new drugs, or; (2) a phytomedicine to be used for the treatment of disease. There are numerous illustrations of plant derived drugs. Some selected examples, including those classified as antiinfective, are presented below. The isoquinoline alkaloid emetine obtained from the underground part of Cephaelis ipecacuanha, and related species, has been used for many years as and amoebicidal drug as well as for the treatment of abscesses due to the spread of Escherichia histolytica infections. Another important drug of plant origin with a long history of use, is quinine. This alkaloid occurs naturally in the bark of Cinchona tree. Apart from its continued usefulness in the treatment of malaria, it can be also used to relieve nocturnal leg cramps. Currently, the widely prescribed drugs are analogs of quinine such as chloroquine. Some strains of malarial parasites have become resistant to the quinines, therefore antimalarial drugs with novel mode of action are required.

The use of and search for drugs and dietary supplements derived from plants have accelerated in recent years. Ethnopharmacologists, botanists, microbiologists, and natural-products chemists are combing the Earth for phytochemicals and “leads” which could be developed for treatment of infectious diseases. While 25 to 50% of current pharmaceuticals are derived from plants, none are used as antimicrobials. Traditional healers have long used plants to prevent or cure infectious conditions; Western medicine is trying to duplicate their successes. Plants are rich in a wide variety of secondary metabolites, such as tannins, terpenoids, alkaloids, and flavonoids, which have been found in vitro to have antimicrobial properties. This review attempts to summarize the current status of botanical screening efforts, as well as in vivo studies of their effectiveness and toxicity. The structure and antimicrobial properties of phytochemicals are also addressed. Since many of these compounds are currently available as unregulated botanical preparations and their use by the public is increasing rapidly, clinicians need to consider the consequences of patients self-medicating with these preparations.

Major classes of antimicrobial compounds from plants

Clin Microbiol Rev. 1999 October; 12(4): 564–582. Copyright © 1999, American Society for Microbiology

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