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Biotransformation of Xenobiotics in Living Systems—Metabolism of Drugs: Partnership of Liver and Gut Microflora
Published in Peter Grunwald, Pharmaceutical Biocatalysis, 2020
First examples of drug conjugates possessing sulfate, glucuronic acid, methyl and acetylated moieties were discovered in the mid-1800s, realizing that they are less toxic compared to parent compound and metabolites of phase I. Phase II biotransformation is catalyzed by the enzymes which are collectively known as “transferases” as they catalyze the transfer of a moiety from a donor molecule to the drug recipient (uridine diphosphate (UDP)-glucuronosyltransferases (UGTs), sulfotransferases, N-acetyltransferases (arylamine N-acetytransferase; NATs), glutathione (GSH) S-transferases (GSTs) and various methyltransferases) (Omiecinski et al., 2011). Phase II enzymes can directly interact with xenobiotics but more commonly interact with the newly formed functional group of metabolites produced by phase I reactions (Croom, 2012). Since many metabolites of phase I are too lipophilic to be retained in the kidney tubules, a subsequent conjugation reaction with an endogenous substrate, such as glucuronic acid, acetic acid, sulfuric acid or an amino acid, results in formation of more polar and hydrophilic compounds that are sufficiently polar to be excreted by the kidneys. These reactions represent the real drug detoxification pathways since the most common outcome of phase II reactions is the production of therapeutically inactive conjugates (Omiecinski et al., 2011). An important exception is morphine-6-glucuronide, a widely used opioid analgesic and the most cited example of a pharmacologically active glucuronide which is twice as potent as parent morphine in many models of analgesia (Christrup, 1997). Although phase II reactions most commonly follow phase I, not all drugs undergo reactions in that order. For example, the major pathways of isoniazid metabolism include acetylation, in the first place, forming acetyil-isoniazid by means of NAT, followed by hydrolysis to produce isonicotinic acid by means of amidase (Wang et al., 2016).
Aesculus indica: an updated review on its pharmacognosy, phytochemistry and pharmacological profile
Published in Egyptian Journal of Basic and Applied Sciences, 2022
Neha Yadav, Aakash Partap Singh, Avtar Chand Rana, Sunil Kumar, Prabhjeet Kaur, Jitender Singh, Ashok Jangra, Dinesh Kumar
Traditional medicine is a broad term used to describe medicine from earth’s natural resources that includes Unani, Chinese, Ayurvedic and Siddha system of medicines [1]. More than 50% medications of clinical use in the world are based on natural products and their derivatives [2]. According to a survey of World Health Organization (WHO) in developing countries, 80% of population rely on medicines derived from plants [3]. It has been reported that 21,000 plants possess medicinal properties, out of which 3,000 species are found in India [4]. In India, Eastern Himalayan region is the richest one on the earth for valuable medicinal plants. As compared to synthetic drugs, plant-based compounds are less toxic and more effective. However, solubility and bioavailability are one of the major problems in the drug development process of phytochemicals. These problems can be overcome by using novel formulation technologies that can facilitate potential health benefits of bioactive compounds of plants. In recent years, awareness about the benefits of medicinal plants and their by-products in health and diseases has been continuously increasing [5. Natural products have a major contribution to the advancement of modern medicine. The market pharmaceutical agents such as antibiotics, anticancer agents, anti-inflammatory compounds and analgesics have been discovered as a result of the quest for new therapeutics leads from natural resources, which has lasted for centuries (6]. Medicinal plant derivatives are in high demand around the world as a first-line treatment for human health. India has been named as the ‘Medicinal Garden of the World’ due to the presence of high diversity in medicinal plants [7]. Huge breakthroughs in therapy were achieved from the development of some highly potent drugs during this period, which includes tiotropium and ipratropium for chronic obstructive pulmonary disease (Atropa belladonna; Solanaceae), morphine-6-glucuronide, potent analgesia (Papaver somniferum L.; Paparveraceae), exatecan for cancer (Camptotheca acuminate; Nyssaceae), vinflunine and modified vinblastine, for cancer (Catharanthus roseus; Apocynaceae) [8] There are numerous compounds of therapeutic importance that have been once obtained from plant sources but now are being produced commercially. They include caffeine, theophylline, ephedrine, pseudoephedrine, emetine, papaverine, L-dopa, salicylic acid and tetrahydrocannabinol [9]. Aesculus indica (A. Indica) consists of 20 species, which is spread mainly in the colder region all over the world and belongs to the Hippocastanacea family. It is widely used in folk medicines due to its medicinal properties. Seeds, bark and roots are used for rheumatism; fruits are used as anti-diabetic and in colic disorder; leaves possess anti-cancer properties [10]. It is highly useful in hemorrhoids, varicose veins and ulcers to prevent thrombosis. It often aids in the treatment of migraine, blood effusions and frost bite [11]. The present review highlights the geographical, historical, botanical and pharmacological perspectives of Aesculus indica.