Common Garlic (Allium sativumL.) has Potent Anti-Bacillus anthracisActivity

AbstractEthnopharmacological RelevanceGastrointestinal anthrax, a disease caused byBacillus anthracis, remains an important but relatively neglected endemic disease of animals and humans in remote areas of the Indian subcontinent and some parts of Africa. Its initial symptoms include diarrhea and stomachache. In the current study, several common plants indicated for diarrhea, dysentery, stomachache or as stomachic as per traditional knowledge in the Indian subcontinent,i.e.,Aegle marmelos(L.) Correa (Bael),Allium cepaL. (Onion),Allium sativumL. (Garlic), Azadirachta indicaA. Juss. (Neem),Berberis asiaticaRoxb. ex DC. (Daruharidra),Coriandrum sativumL. (Coriander),Curcuma longaL. (Turmeric),Cynodon dactylon(L.) Pers. (Bermuda grass),Mangifera indica L.(Mango),Morus indicaL. (Black mulberry),Ocimum tenuiflorumL.(Ocimum sanctum L., Holy Basil),Ocimum gratissimumL. (Ram Tulsi),Psidium guajavaL. (Guava),Zingiber officinaleRoscoe (Ginger), were evaluated for their anti-Bacillus anthracisproperty. The usage ofAzadirachta indicaA. Juss. andCurcuma longaL. by Santals (India), andAllium sp.by biblical people to alleviate anthrax-like symptoms is well documented, but the usage of other plants is traditionally only indicated for different gastrointestinal disturbances/conditions.Aim of the StudyEvaluate the above listed commonly available edible plants from the Indian subcontinent that are used in the traditional medicine to treat gastrointestinal diseases including those also indicated for anthrax-like symptoms for the presence of potent anti-B. anthracisactivity in a form amenable to use by the general population in the endemic areas.Materials and MethodsAqueous extracts made from fourteen plants indicated above were screened for their anti-B. anthracisactivity using agar-well diffusion assay (AWDA) and broth microdilution methods. The Aqueous Garlic Extract (AGE) that displayed most potent anti-B. anthracisactivity was assessed for its thermostability, stability under pH extremes encountered in the gastrointestinal tract, and potential antagonistic interaction with bile salts as well as the FDA-approved antibiotics used for anthrax control. The bioactive fractions from the AGE were isolated by TLC coupled bioautography followed by their characterization using GC-MS.ResultsGarlic (Allium sativumL.) extract was identified as the most promising candidate with bactericidal activity againstB. anthracis. It consistently inhibited the growth ofB. anthracisin AWDA and decreased the viable colony-forming unit counts in liquid-broth cultures by 6-logs within 6-12 h. The AGE displayed acceptable thermostability (>80% anti-B. anthracisactivity retained on incubation at 50°C for 12 h) and stability in gastric pH range (2-8). It did not antagonize the activity of FDA-approved antibiotics used for anthrax control. GC-MS analysis of the TLC separated bioactive fractions of AGE indicated the presence of previously unreported constituents such as phthalic acid derivatives, acid esters, phenyl group-containing compounds, steroidsetc.ConclusionThe Aqueous Garlic Extract (AGE) displayed potent anti-B. anthracisactivity. It was better than that displayed byAzadirachta indicaA. Juss. (Neem) andMangifera indicaL. whileCurcuma longaL. (Turmeric) did not show any activity under the assay conditions used. Further work should be undertaken to explore the possible application of AGE in preventing anthrax incidences in endemic areas.Abstract Figure