Securinine, isolated from Securinega suffruticosa Rehd, is similar to strychnine in action, but exhibits lower toxicity, stimulates respiration, raises blood pressure, and increases cardiac output. The chemistry, pharmacology, and biosynthesis of securinine and related compounds have been reviewed.

Tryptophan-Derived Alkaloids

Tryptophan-derived alkaloids, which occur in the families Apocynaceae, Rubiaceae, and Loganiaceae, have recently become of great interest, particularly those derived from tryptamine and a monoterpene unit. There are many diverse structural types in this group. Attempts to determine the important details of the biosynthetic interconversions of these compounds have been reported.

The simplest indole alkaloids are derived from tryptamine itself. These include indole-3-acetic acid, a potent plant-growth stimulator; serotonin (5-hydroxytryp-tamine), a vital mammalian product that inhibits or stimulates smooth muscles and nerves; AT-acetyl-5-methoxy-tryptamine (melotonin), a constituent of the pineal gland with melanophase-stimulating properties; 5-methoxy-Ar,AT-dimethyltryptamine, a constituent of the hallucinogenic Virola snuffs; psilocybine, a hallucinogenic found in the mushroom Psilocybe mexicana Heim.

The harmala alkaloids, such as harmine and harma-line, are powerful monoamine oxidase inhibitors, previ ously used in the treatment of Parkinsonism. Harmine is the active ingredient of the narcotic drug yage.

Ellipticine and derivatives show anticancer activity.

Several alkaloids of Calycanthus spp. are the products of dimerization or trimerization of simple tryptamine residues, such as folicanthine.

The main indole alkaloid skeletons are derived from tryptamine and a C10 unit. Examples include corynan-thine; yohimbine, which has hypotensive and cardiostimulant properties and is used to treat rheumatic disease; ajmaline, which has coronary dilating and antiarrhythmic properties; decarbomethoxydihydrovobasine, which shows vasodilating and hypotensive activities whereas related compounds exhibit antiviral activity; akuammicine; tabersonine; catharanthine; rhynchophyl-line; vindoline; dihydrovobasine; 10-methoxyibogamine, whose acyl derivatives exhibit analgesic and antiinflammatory activity; and strychnine. This structural diversity has been the source of intense biosynthetic interest.


Physostigmine, found in the perennial West African woody climber, Physostigma venenosum Balfour, is pharmacologically similar to pilocarpine and is a reversible Cholinesterase inhibitor used to treat glaucoma.

The Ergot Alkaloids

The ergot alkaloids are obtained from ergot, the dried Sclerotium of the fungus Claviceps purpurea (Fries) Tulsane (Hypocreaceae). Ergot alkaloids are produced by isolation from the crude drug grown in the field, by extraction from saprophytic cultures, and by partial and total synthesis.

The ergot alkaloids act pharmacologically to produce peripheral, neurohormonal, and adrenergic blockage, and to produce smooth-muscle contraction as well. The two medicinally important ergot alkaloids are ergotamine and er-gonovine.

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