August 19, 2016

Orchid phytochemicals

Diverse species of orchids from the Indian subcontinent and the Americas. Photo: Saikat Kumar Basu
Diverse species of orchids from the Indian subcontinent and the Americas. Photo: Saikat Kumar Basu

Orchids constitute a widely diverse group of plants distributed across the tropics and sub-tropics of Asia, Africa, Latin America and Australia; as well as some of the temperate regions of Asia, Europe and the Americas. Orchids belong to the plant family Orchidaceae; and are one of the largest groups of flowering plants in the planet closely competing with plants of the sunflower family (Astercaeae) in sheer numbers and diversity. Orchids are predominantly herbaceous plants and a vast number of them is epiphytic in nature meaning they grow harmlessly on other plants for protection and survival without acting as a parasite on their host. The members of this plant family are known for their spectacular beauty and diversity of their floral forms, color and patterns and hence serve as highly sought after ornamental species across the globe and have huge financial returns in the global floral markets. In additional to ecological, ornamental and horticultural values, the plant family is also known to be industrially important; particularly for the commercial production of the essence vanilla, widely used in the confectionary industries across the globe obtained from the plant Vanilla planifolia and allied species.
Several species of orchids are reported globally to be medicinally important and have been reported to have rich pharmacological properties. Several such orchids have been traditionally used by numerous aboriginal communities and tribal members across the globe for treatment of a wide number of human diseases such as asthma, fever, menstrual disorders, epilepsy, rheumatism, skin diseases, malaria, dysentery, diarrhea, nausea and vomiting, tuberculosis, gout, heart, liver and kidney disorders, in the healing of wounds and infections due to injuries and several other diseases.

“The renewed interest in the orchids for exploring their medicinal properties and with latest discoveries of rich phytochemicals in several orchid species has made them vulnerable to ruthless exploitations threatening their existence.”

In most cases phytochemical investigations of the orchid leaves, roots, tubers, floral petals and fruits extracts have successfully revealed different medicinal properties. Different forms of orchid tissue extracts (such as aqueous, methanol, ethanol, petroleum ether, hexane and chloroform) have been experimented with; and they have demonstrated various levels of promising anti microbial properties against different strains of pathogenic bacteria and fungi in several species of orchids being investigated across the globe.  For example, anti microbial properties of several orchid species against important human pathogens have been found to increasingly successful against bacteria like Streptococcus mutans, Streptococcus pneumonia, Micrococcus sp., Staphylococcus aureus, Bacillus subtilis, Escherichia coli, Pseudomonas aeruginosa, Entrobacter faecalis, Salmonella typhi, Salmonella paratyphi, Shigella flexneri, Klebsiella  pneumoniae; and fungi like Candida albicans, yeast (Saccharomyces sp., Schizosaccharomyces sp) and different mold species (Trichophyton, Mucor etc).
The alarming rise in drug (particularly antibiotics) resistant microbes has been pushing the pharmaceutical industries across the globe to push for the search and screening of potential new drugs, therapeutics and in identifying and isolating novel phytochemicals for generating better, more affective antimicrobials. Pharmacognosy studies (studies of drugs from various natural sources including plants) on orchids have become increasingly popular globally in laboratories specializing in plant chemistry. Due to the detection of several phytochemicals in various orchid species they are also been simultaneously being investigated for their potential for use in the nutraceutical and functional food industries.
Several species of orchids have been investigated and some have clearly shown great promises with respect to presence of important phytochemicals as well as significant anti microbial (both antifungal and antibacterial), anti oxidant, anti pyretic, anti tumor, anti inflammatory, anthelmintic and nutraceutical properties such as  medicinally important species like Dendrobium nobile, Calyptrochilum emarginatum, Satyrium  nepalense. Rhynchostylis retusa, Eulophia nuda, Bulbophyllum kaitense to name only a few.  Conventional and advanced chromatographic methods have been successful in identifying and quantifying several phytochemicals from different orchid species like different carbohydrates, amino acids, tannins, flavones, flavonoids, flavonones, phenols, coumarins, quinine, terpenes, triterpenes, sterols, saponins, alkaloids, glycosides (cardiac glycosides) etc.
However, this good news is also associated with some unfortunate incidents. The renewed interest in the orchids for exploring their medicinal properties and with latest discoveries of rich phytochemicals in several orchid species has made them vulnerable to ruthless exploitations threatening their existence. The situation is particularly alarming in the biodiversity hot beds of developing and under developed nations that are economically under developed but are rich in orchid diversity. Several species of orchids many of them endemic (not found anywhere else other than their native habitats) are being illegally exploited and harvested and even collected for the under ground nursery industries.
As a consequence several such rare and economically and medicinally important orchid species have been pushed towards extinction and are either placed under either vulnerable or threatened, nearly threatened; endangered or critically endangered status due to such indiscriminate poaching and harvesting. Orchids are considered as flag ship species from a plant perspective in any major ecosystems. If the status of orchids is degraded; sooner or later the remaining ecosystems will also become vulnerable to anthropogenic pressures without intervention. Hence, while it is important to identify the orchid species with potential anti microbial properties and those that are rich in different pharmaceutically important phytochemicals; however, it is also important to conserve these valuable species from over exploitations for our future generations through comprehensive, long term and sustainable planning for protecting and conserving them.


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