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.

Plant Products as Antimicrobial Agents

The biochemistry and medical significance of the flavonoids.

In vitro antiplasmodial activity of medicinal plants native to or naturalised in South Africa.

The antimicrobial activity and Minimal Inhibitory Concentration (MIC) of the extracts of Bidens pilosa L, Bixa orellana L, Cecropia peltata L, Cinchona officinalis L, Gliricidia sepium HB & K, Jacaranda mimosifolia DDon, Justicia secunda Vahl, Piper pulchrum CDC, P paniculata L and Spilanthes americana Hieron were evaluated against five bacteria (Staphylococcus aureus, Streptococcus β hemolitic, Bacillus cereus, Pseudomonas aeruginosa, and Escherichia coli), and one yeast (Candida albicans) These plants are used in Colombian folk medicine to treat infections of microbial origin Plants were collected by farmers and traditional healers The ethanol, hexane and water extracts were obtained by standard methods The antimicrobial activity was found by using a modified agar well diffusion method All microorganisms were obtained from the American Type Culture Collection (ATCC) MIC was determined in the plant extracts that showed some efficacy against the tested microorganisms Gentamycin sulfate (10 μg/ml), clindamycin (03 μg/ml) and nystatin (10 μg/ml) were used as positive controls The water extracts of Bidens pilosa L, Jacaranda mimosifolia DDon, and Piper pulchrum CDC showed a higher activity against Bacillus cereus and Escherichia coli than gentamycin sulfate Similarly, the ethanol extracts of all species were active against Staphylococcus aureus except for Justicia secunda Furthermore, Bixa orellana L, Justicia secunda Vahl and Piper pulchrum CDC presented the lowest MICs against Escherichia coli (08, 06 and 06 μg/ml, respectively) compared to gentamycin sulfate (09 8g/ml) Likewise, Justicia secunda and Piper pulchrum CDC showed an analogous MIC against Candida albicans (05 and 06 μg/ml, respectively) compared to nystatin (06 μg/ml) Bixa orellana L, exhibited a better MIC against Bacillus cereus (02 μg/ml) than gentamycin sulfate (05 μg/ml) This in vitro study corroborated the antimicrobial activity of the selected plants used in folkloric medicine All these plants were effective against three or more of the pathogenic microorganisms However, they were ineffective against Streptococcus β hemolytic and Pseudomonas aeruginosa Their medicinal use in infections associated with these two species is not recommended This study also showed that Bixa orellana L, Justicia secunda Vahl and Piper pulchrum CDC could be potential sources of new antimicrobial agents

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Screening for antimicrobial activity of ten medicinal plants used in Colombian folkloric medicine: A possible alternative in the treatment of non-nosocomial infections

Background
In traditional medicine whole plants or mixtures of plants are used rather than isolated compounds. There is evidence that crude plant extracts often have greater in vitro or/and in vivo antiplasmodial activity than isolated constituents at an equivalent dose. The aim of this paper is to review positive interactions between components of whole plant extracts, which may explain this.

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Whole plant extracts versus single compounds for the treatment of malaria: synergy and positive interactions

Antimalarial activity of extracts and fractions from Bidens pilosa and other Bidens species (Asteraceae) correlated with the presence of acetylene and flavonoid compounds

C.G.C. Nery

Papers

Antimalarial activity of extracts and fractions from Bidens pilosa and other Bidens species (Asteraceae) correlated with the presence of acetylene and flavonoid compounds

Two methoxylated flavone glycosides from Bidens pilosa