Reserpine is an alkaloid, isolated from the Rauwolfia serpentina plant and developed by Ciba pharma. Reserpine was approved by FDA for the treatment of hypertension and psychotic disorders. The drug exerts its effect by blocking two vesicular monoamine transporters, VMAT1 and VMAT2. The blockade results in vesicles that lose their ability to store neurotransmitter molecules. Neurotransmitters, thus retained in cytosol, are then neutralized by MAO.

Digoxin is a cardiac glycoside derived from the purple foxglove flower. In 1785, the English chemist, botanist, and physician Sir William Withering published his findings that Digitalis purpurea could be used to treat cardiac dropsy (congestive heart failure; CHF). Digoxin has been in use for many years, but was not approved by the FDA for treatment of heart failure (HF) until the late 1990s. Another FDA indication for digoxin is atrial fibrillation (AF). Digoxin also has numerous off-label uses, such as in fetal tachycardia, supra-ventricular tachycardia, cor pulmonale, and pulmonary hypertension. Digitoxin inhibits the Na-K-ATPase membrane pump, resulting in an increase in intracellular sodium and calcium concentrations. Increased intracellular concentrations of calcium may promote activation of contractile proteins (e.g., actin, myosin). Digoxin also has Para sympathomimetic properties. By increasing vagal tone in the sinoatrial and atrioventricular (AV) nodes, it slows the heart rate and AV nodal conduction.

Piperidolate hydrochloride is an antimuscarinic, inhibits intestinal cramp induced by acetylcholine (rats and dogs. It’s usually used to kill the cramp-like pain of gastric/duodenal ulcer, gastritis, enteritis, gallstones, cholecystitis and biliary tract dyskinesia and to improve some symptoms in threatened miscarriage/premature delivery. Piperidolate blocked the contraction of ACh, Ba ++ and electrical stimulations on the isolated rat, mouse and guinea-pig ileum and trachea. In guinea-pig teania caeci, piperidolate like papaverine blocked specifically the tonic response, however, piperidolate in high doses completely blocked both spike and tonic responses. These results indicate that spasmolytic action of piperidolate like that of papaverine may depend upon inhibition of the release of store Ca++. Moreover piperidolate, given at high doses, may inhibit the contractile elements in the smooth muscle. In the rat uterus pretreated with sex hormones, piperidolate nonspecifically blocked the contraction of ACh, Ba ++ and oxytocin and sex hormones had no influence on the spasmolytic action of piperidolate.

Thiamylal is a barbiturate that is administered intravenously for the production of complete anesthesia of short duration, for the induction of general anesthesia, or for inducing a hypnotic state. Thiamylal, a barbiturate, is used in combination with acetaminophen or aspirin and caffeine for its sedative and relaxant effects in the treatment of tension headaches, migraines, and pain. Barbiturates act as nonselective depressants of the central nervous system (CNS), capable of producing all levels of CNS mood alteration from excitation to mild sedation, hypnosis, and deep coma. In sufficiently high therapeutic doses, barbiturates induce anesthesia. Thiamylal binds at a distinct binding site associated with a Cl- ionopore at the GABAA receptor, increasing the duration of time for which the Cl- ionopore is open. The post-synaptic inhibitory effect of GABA in the thalamus is, therefore, prolonged.

Iodipamide is used as a contrast agent for cholecystography and intravenous cholangiography. Following intravenous administration of Cholografin Meglumine, iodipamide is carried to the liver where it is rapidly secreted. The contrast medium appears in the bile within 10 to 15 minutes after injection, thus permitting visualization of the hepatic and common bile ducts, even in cholecystectomized patients. Iodipamide (Cholografin Meglumine) is indicated for intravenous cholangiography and cholecystography as follows: (a) visualization of the gallbladder and biliary ducts in the differential diagnosis of acute abdominal conditions, (b) visualization of the biliary ducts, especially in patients with symptoms after cholecystectomy, and (c) visualization of the gallbladder in patients unable to take oral contrast media or to absorb contrast media from the gastrointestinal tract. The biliary ducts are readily visualized within about 25 minutes after administration, except in patients with impaired liver function. The gallbladder begins to fill within an hour after injection; maximum filling is reached after two to two and one-half hours. Organic iodine compounds block x-rays as they pass through the body, thereby allowing body structures containing iodine to be delineated in contrast to those structures that do not contain iodine. The degree of opacity produced by these iodinated organic compounds is directly proportional to the total amount (concentration and volume) of the iodinated contrast agent in the path of the x-rays. Iodipamide's primary excretion through the hepato-biliary system and concentration in bile allows visualization of the gallbladder and biliary ducts.

Quercetin is a unique bioflavonoid that has been extensively studied by researchers over the past 30 years. Quercetin, the most abundant of the flavonoids (the name comes from the Latin –quercetum, meaning oak forest, quercus oak) consists of 3 rings and 5 hydroxyl groups. Quercetin is a member of the class of flavonoids called flavonoles and forms the backbone for many other flavonoids including the citrus flavonoids like rutin, hesperidins, Naringenin and tangeritin. It is widely distributed in the plant kingdom in rinds and barks. The best described property of Quercetin is its ability to act as antioxidant. Quercetin seems to be the most powerful flavonoids for protecting the body against reactive oxygen species, produced during the normal oxygen metabolism or are induced by exogenous damage [9, 10]. One of the most important mechanisms and the sequence of events by which free radicals interfere with the cellular functions seem to be the lipid peroxidation leading eventually the cell death. To protect this cellular death to happen from reactive oxygen species, living organisms have developed antioxidant line of defense systems [11]. These include enzymatic and non-enzymatic antioxidants that keep in check ROS/RNS level and repair oxidative cellular damage. The major enzymes, constituting the first line of defence, directly involved in the neutralization of ROS/RNS are: superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx) The second line of defence is represented by radical scavenging antioxidants such as vitamin C, vitamin A and plant phytochemicals including quercetin that inhibit the oxidation chain initiation and prevent chain propagation. This may also include the termination of a chain by the reaction of two radicals. The repair and de novo enzymes act as the third line of defence by repairing damage and reconstituting membranes. These include lipases, proteases, DNA repair enzymes and transferases. Quercetin is a specific quinone reductase 2 (QR2) inhibitor, an enzyme (along with the human QR1 homolog) which catalyzes metabolism of toxic quinolines. Inhibition of QR2 in plasmodium may potentially cause lethal oxidative stress. The inhibition of antioxidant activity in plasmodium may contribute to killing the malaria causing parasites.

Protoveratrine B is one of two alkaloids isolated from the plant Veratrum albumen. The main effect of both alkaloids is vasodilation in all vascular beds thereby reducing blood pressure. In the 1950's it was recognized that Protoveratrine B is the preferred compound which can be administered at significantly higher doses before the patient begins to vomit.

Protoveratrine A, the principal alkaloid of Veratrum album, has been used in the treatment of hypertension but has largely been replaced by drugs with fewer adverse effects.

Diethylcarbamazine is used in humans, dogs and cats for the treatment of parasitic infections, including pulmonary eosinophilia, loiasis, and lymphatic filariasis. The exact mechanism of its action is unknown, however some studies showed the involvment of inducible nitric-oxide synthase and the cyclooxygenase pathway. Although there is no information on whether the drug is marketed in the USA and Europe, it is currently used in India.

Khellin is a crystalline extract of a crude drug, which has long been used in Egypt for the treatment of ureteral colic. It is used in the management of bronchial asthma and angina pectoris. Interest in khellin as an adjunct to ultraviolet (UV) light therapy in the treatment of vitiligo is based on the structural similarity between khellin and the psoralens. Success has been reported using oral and topical khellin in clinical studies but it is not likely that khellin will be approved for the treatment of vitiligo. Unwanted side effects of khellin include dizziness, reversible cholestatic jaundice, pseudoallergic reaction, and elevated levels of liver enzymes (transaminases and gamma-glutamyltransferase).