Pharmacology of Poppy Alkaloids: Major Opium Alkaloids

 The latex obtained by the incision of unripe seed capsules of Papaver somniferum and which is known as opium is the source of several pharmacologically important alkaloids. Dioskorides, in about AD 77, referred to both the latex (opos) and the total plant extract (mekonion) and to the use of oral and inhaled (pipe smoked) opium to induce a state of euphoria and sedation. Since before the Christian era the therapeutic properties of opium were evident, with the first written reference to poppy juice by Theophrastus in the third century BC. Powdered opium contains more than 40 alkaloids which constitute about 25% by weight of the opium and are responsible for its pharmacological activity. In 1803 the German pharmacist Sertiirner achieved the isolation of morphine as one of the active ingredients of opium. Morphine, codeine, thebaine, papaverine, narcotine and narceine are the most important bases, with many of the remaining (minor) alkaloids occurring only in traces. Morphine Morphine has long occupied an eminent position on the list of useful drugs. As a pure alkaloid, it has been employed for over a century and a half and, as the most important constituent of opium, it has contributed to the comfort of the human Read more […]

Mucuna pruriens

Importance of L-DOPA A hypofunction of the nigrostriatal and the mesolimbic dopaminergic systems appears to cause the symptoms of Parkinson’s disease (e.g. tremor, rigidity, akinesia). Post mortem studies have revealed a severe degradation of melanin-containing neurons in the substantia nigra zona compacta and a marked reduction of the contents of dopamine, its synthesizing enzymes and metabolites in various brain areas of Parkinsonian patients. Both precursors in the biosynthesis of L-DOPA, i.e. L-tyrosine and 3-(3,4-dihydroxyphenyl)-L-alanine (L-DOPA), may be taken up from the bloodstream by the brain. Dopamine is not able to pass the blood/liquor barrier. For this reason, L-DOPA has found a wide application for the symptomatic relief of Parkinson’s disease. At present, commercially available L-DOPA is being synthesized chemically starting from vanillin. Due to its relatively great demand, a continuous search for alternative production possibilities is being carried out. Among these are the use of fungi for the bioconversion of N-formyltyrosine or N-carbobenzoxy-L-tyrosine, and the enzymatic coupling of DL-serine and pyrocatechol by tyrosine phenol lyase. Occurrence of L-DOPA in Plants The occurrence of L-DOPA Read more […]

DOPAMINE RECEPTOR AGONISTS

DOPAMINE RECEPTOR AGONISTS act to stimulate dopamine receptors, and these have a major neurotransmitter role in the CNS. Dopamine is also a precursor in the formation of the catecholamine monoamine neurotransmitter noradrenaline and the hormone adrenaline. The distribution of dopamine in the brain is very non-uniform. There is some in the limbic system, and a large proportion is found in the corpus striatum — a part of the extrapyramidal motor system which is concerned with the coordination of movement. Dopamine-containing nerves are found in three main pathways in the brain. The nigrostriatal pathway contains about 75% Of the dopamine in the brain, and the cell bodies lie in the substantia nigra and the nerves terminate in the corpus striatum. The second important pathway is the mesolimbic pathway, the cell bodies of which lie in the mid-brain and project to parts of the limbic system, particularly the nucleus accumbens. The third, the tubero-infundibular system, consists of short neurons that run from the arcuate nucleus of the hypothalamus to the median eminence and the pituitary gland, the secretions of which they regulate. With respect to disturbances of dopamine neurotransmitter function, the first-mentioned Read more […]

Nervous Affections

There are writers other than Grieve who consider mugwort a nervine. Ibn Sina records the benefit of artemisia in headache due to a cold cause and in nasal catarrh while the Salernitan herbal, reflecting Arabic influences, recommends a hot opiate taken with a decoction of artemisia for migraine. Bauhin cites the empiric Wirtemberg, who guarantees relieving within an hour a headache due to cold by washing the head with a decoction of mugwort in wine, then laying on the hot leaves. This is a version of a cure for migraine from Arnold de Villanova, Bauhin points out, mentioning also that mugwort in wine or lavender water can be used in cases of paralysis. Other uses in Bauhin’s day include inducing sleep, treating scabs on the head, clearing jaundice and preventing dropsy, and reversing prolapse of the anus. In this last case, the anus is first fumigated with myrrh Commiphora molmol and colophonia before a hot poultice of mugwort cooked in red wine is applied. Quincy classifies uterine medicines under nervous simples, where these ‘hysterics’ must be differentiated from carminatives and from cephalics and cordials, now under one heading for ‘what is cordial must be cephalic as the head hath a principal share in agreeable Read more […]

Normal Sexual Function

Penile erection is initiated by neuropsychological stimuli that ultimately produce vasodilation of the sinusoidal spaces and arteries within the paired corpora cavernosa. Erection is normally preceded by sexual desire (or libido), which is regulated in part by androgen-dependent psychological factors. Although nocturnal and diurnal spontaneous erections are suppressed in men with androgen deficiency, erections may continue for long periods in response to erotic stimuli. Thus, the continuing action of testicular androgens appears to be required for normal libido but not for the erectile mechanism itself. The penis is innervated by sympathetic, parasympathetic, and somatic fibers. Somatic fibers in the dorsal nerve of the penis form the afferent limb of the erectile reflex by transmitting sensory impulses from the penile skin and glans to the S2-S4 dorsal root ganglia via the pudendal nerve. Unlike the corpuscular-type endings in the penile shaft skin, most afferents in the glans terminate in free nerve endings. The efferent limb begins with parasympathetic preganglionic fibers from S2-S4 that pass in the pelvic nerves to the pelvic plexus. Sympathetic fibers emerging from the intermediolateral gray areas of T11-L2 Read more […]

LIGNANS AND LIGNINS

Lignans are composed of two phenylpropanoid units joined together to form an 18-carbon skeleton. Many other functional groups can then be added by the plant to modify this base structure. Generally, these molecules are lipophilic and function within plant cell membranes to provide rigidity, strength, and water impermeability. Most lignans are relatively safe. Few generalizations can be made about this class of compounds beyond these statements, in part because of the lack of research. As interest in lignans grows, more information will surely become available. Several lignans have demonstrated intriguing and important clinical activity. Podophyllotoxin from Podophyllum peltatum (mayapple) acts as a cathartic laxative that is distinct from the anthraquinone glycosides; it inhibits human papillomavirus (HPV) and is antineoplastic. The semisynthetic chemotherapy drugs teniposide and etoposide are derived directly from this molecule. The lignans in Linum usitatissimum (flax), such as sec-oisolariciresinol, are transformed by the gut flora to enterodiol and enterolactone, known phytoestrogenic constituents that clearly are active in vivo. Flax seeds have definite anticancer effects, as has been documented in the results Read more […]

CALCIUM-CHANNEL BLOCKERS

CALCIUM-CHANNEL BLOCKERS are agents that literally block or close any of the many types of calcium channels. However, in common usage the term is mainly used to describe a class of drugs finding increasing application in therapeutics (also called calcium antagonists or calcium-entry blockers) typified by the dihydropyridines (DHPs). In a more general usage of the term, there are many different classes of calcium-channel blockers, and many types of calcium channels. See CALCIUM-CHANNEL ACTIVATORS. First, in the cell membrane, the voltage-gated calcium channels are of at least six types — termed L, N, T, P, Q, R — that may be differentiated by electrophysiological, molecular cloning and pharmacological criteria. The L- and N-channels are high-voltage activated, voltage-dependent and undoubtedly of great importance in normal physiology; L mainly in smooth, cardiac and skeletal muscle (and some neurons), but N only in neurons. T-channels are important in repetitive activity in cardiac SA node of the heart, neurons and some endocrine cells. The remainder have been found more recently in neurons. These channels are products of different genes, but they all share great structural similarity — both with respect to Read more […]

Korean ginseng: Clinical Use

In the scientific arena, ginseng and the various ginsenosides are used in many forms and administered via various routes. This review will focus primarily on those methods commonly used in clinical practice. CANCER PREVENTION The various anticancer actions of Panax ginseng, as demonstrated in animal and in vitro trials, support its use as an agent to prevent the development and progression of cancer. A 5-year prospective study of 4634 patients over 40 years of age found that ginseng reduced the relative risk of cancer by nearly 50%. A retrospective study of 905 case-controlled pairs taking ginseng showed that ginseng intake reduced the risk of cancer by 44% (odds ratio equal to 0.56). The powdered and extract forms of ginseng were more effective than fresh sliced ginseng, juice or tea. The preventative effect was highly significant (P < 0.001). There was a significant decline in cancer occurrence with increasing ginseng intake (P < 0.05). Epidemiological studies in Korea strongly suggest that cultivated Korean ginseng is a non-organ-specific human cancer preventative agent. In case-control studies, odds ratios of cancer of lip, oral cavity and pharynx, larynx, lung, oesophagus, stomach, liver, pancreas, Read more […]