C. L. Abayasekara

The role of herbometallic preparations in traditional medicine – A review on mica drug processing and pharmaceutical applications

ETHNOPHARMOCOLOGICAL RELEVANCE Biotite mica enriched with Fe(2+) ions are widely used as a major mineral ingredient in traditional pharmaceutical science of alchemy (Rasashastra). Abhrak bhasma (mica ash), a pharmaceutical product containing treated mica, is utilized, for example, in Ayurvedic treatments for ailments such as gastritis, renal disease, skin disease and mainly in rejuvenation formulations. However, the untreated mica minerals may be harmful when used directly, as they carry considerably high amounts of trace-elements that can cause undesirable effects in the human body. In order to remove toxic factors and produce readily absorbable materials having high nutrient capacity, specific thermal and chemical treatments (purification, detoxification, particle size reduction and incineration) are performed during the preparation of Rasashastra. This review evaluates the chemical and pharmacological aspects of mica ash as well as the technological aspects of mica ash production. MATERIALS AND METHODS The detailed literature review on the chemistry and scientific basis of mica ash, its preparation techniques, mica alterations and pharmaceutical applications was carried out by using published Ayurvedic text books and research articles, available from Science Direct, on mica minerals, mica ash and their physico-chemical alteration processes and pharmacological applications. RESULTS During the purification and detoxification procedures, heating followed by quenching (in ionic medium) influences the structural distortion and the development of stress-induced cracks and spallations of the micaceous plates. Thus, the efficient diffusion of the external medium takes place at successive heating and quenching steps. Acidic organic liquids and animal byproducts can enhance the cation exchange capacity and solubility of mica. Further, these natural compounds facilitate the removal of toxic-elements in the structure. When treated-mica and paddy husks are tied up in a cloth and squeezed, particle size reduction and further detoxification takes place. Leaching out of oxidized iron coatings is accelerated when the mixtures are immersed in acidic media, by which the filtrate is enriched with oxidized iron-silicate particles. These nano-oxide particles are converted into a more favorable oxidation form for human consumption when the herbometallic mixture is incinerated in closed vessels. Recent analytical data reveals that major and minor elements in mica ash are within the limits of pharmacopoeial standards for Ayurvedic formulations. Further, recent studies show that mica ash has hypoglycemic, hepatoprotective, anthelminthic and antimicrobial properties. CONCLUSIONS Chemical and structural modifications in mica occur during mica-based drug preparation in traditional medicine. Purification steps particularly influence the structural distortion while heating and quenching can form nano-size particles. Carboxylic acids and other organic molecules present in quenching media serve as chemical modifiers of mica. At the same time the toxic elements are leached out from mica to the quenching media through an ion exchange process. Mica ash has been successfully used for treating liver, kidney and skin related ailments in traditional medicine, and mica ash alone or its herbo-metallic formulations have different applications. Further, the recent toxicological and analytical studies validate the traditional uses of mica ash and mica ash bearing products. Further scientific studies are needed to fully establish that mica-based pharmaceuticals are safe and devoid of toxic and long term side effects.

The Role of Pre-formed Antifungal Substances in the Resistance of Fruits to Postharvest Pathogens

Plants contain secondary metabolites with antifungal properties. In fruits they are mostly concentrated in the peel at immature stage and decline during ripening in coincidence with fungal rot development. The information on antifungal systems in immature avocado and mango, reviewed here, suggests that they play a role in natural disease resistance. Immature mangoes have evolved a formidable antifungal system comprising several resorcinols, gallotannins and chitinases. Resorcinols and gallotannins are inhibitory to major postharvest pathogens, Colletotrichum gloeosporioides causing anthracnose and Botryodiplodia theobromae causing stem-end rot. Their levels are generally higher in resistant cultivars than in susceptible ones. Mango latex, distributed in a fine network of canals in the fruit peel, contains chitinases which have the ability to rapidly digest conidia of C. gloeosporioides. Gallotannins and resorcinols decline progressively during ripening and the latex disappears when ripe rot development begins. Retention of latex in the harvested fruit reduces anthracnose and stem-end rot development during ripening. Treatment of harvested fruit with CO2 or inoculation with certain non-pathogenic fungi increased antifungal resorcinol concentration. Immature avocado fruits possess a pre-formed antifungal system comprising at least five antifungal compounds. The quiescence of C. gloeosporioides in the immature fruit has been attributed to the pre-formed antifungal activity of the peel. Lipoxygenase activity increases during fruit ripening, while epicatechin levels decline, suggesting that these events are linked to the decrease in di-ene concentrations. Inhibition of lipoxygenase activity results in retention of antifungal di-ene during ripening increasing fruit resistance. In freshly harvested avocados, the di-ene concentration can be further enhanced by treatment with biotic and abiotic agents.

Antimicrobial potential of two traditional herbometallic drugs against certain pathogenic microbial species.

BackgroundMineral based preparations are widely used for centuries as antimicrobial agents. However, the efficacy and the mode of action of mineral based preparations are uncertain due to the insufficient antimicrobial studies. Arogyawardhana Vati (AV) and Manikya Rasa (MR) are such two Rasashastra herbo-minerallic drugs commonly in India and other countries in South Asia. Despite of their well known traditional use of skin diseases, reported antimicrobial and mineralogical studies are limited. Therefore, in this study antimicrobial activities of the drugs and their organic, inorganic fractions were evaluated against Pseudomonas aeruginosa, Escherischia coli, Staphylococcus aureus, Methecilline Resistance Staphylococcus aureus - MRSA and Candida albicans.MethodsAntimicrobial activity of the drugs, their inorganic residues and organic extracts were determined using four assay techniques viz agar well diffusion, modified well diffusion, Miles and Misra viable cell counting and broth turbidity measurements. Mineralogical constituents of the drugs were determined using X-ray diffraction, while total cation constituents and water soluble cation constituents were determined using inductively coupled plasma-mass spectrometer and the atomic absorption spectrophotometer respectively. Thermogravimetric analysis was used to determine the weight percentages of organic and inorganic fraction of the drugs. Particle sizes of the drugs were determined using the particle size analyzer.ResultsAV and MR drugs showed antibacterial activity against both gram positive and gram negative bacterial species when analyzed separately. Inorganic residues of the drugs and organic extracts showed activity at least against two or more bacterial species tested. All tested components were inactive against C. albicans. Common mineral constituents of drugs are cinnabar, biotite and Fe-rich phases. Drugs were rich in essential elements such as Na, K, Ca, Mg and Fe and toxic elements such as Zn, Cu and As. However, the water soluble concentrations of the toxic elements were below the detection limits. Both drugs have significantly higher percentages of organic constituents and volatile minerals and particle sizes of drugs are in the nanometer range.ConclusionsAV and MR Rasashastra preparations could provide alternatives to synthetic antibiotics against human bacterial infections. Improved solubility and reduced particle sizes are influential physicochemical properties used to enhance the antimicrobial efficacy of the drugs. Therefore, traditional knowledge on the use of antimicrobial mineral sources could provide a novel path for the producing of effective antimicrobial drugs. However, further chemical and toxicological studies are urgently needed for a greater understanding of their toxicity to humans.