Marvin H. Malone

The pharmacological evaluation of natural products — general and specific approaches to screening ethnopharmaceuticals☆

Natural product research is most efficiently conducted in a systematic fashion concentrating on ten critical questions which must be answered in sequential fashion by thoroughly trained professionals experienced in such research. The minimum ethnopharmacology research team should consist of a botanist, a chemist and a pharmacologist with each carrying the responsibility for answering certain of the critical questions. The screening procedures used for the evaluation of synthetic medicinals generally are not appropriate for guiding the extraction of active principles from crude drugs and establishing extraction efficiency; therefore, specialized techniques unique to ethnopharmacology must be used.

Pharmacological and chemical screening of Byrsonima crassifolia, a medicinal tree from Mexico. Part I

Leaf and bark extracts of Byrsonima crassifolia displayed concentration-dependent, spasmogenic effects on rat fundus in vitro and biphasic effects on rat jejunum and ileum in vitro. Dose-related in vivo effects in intact rats using hippocratic screening were: decrease in motor activity, mild analgesia, back tonus, enophthalmos, reversible palpebral ptosis, ear blanching, Robichaud positive, catalepsy (awake) and strong hypothermia. Rat fundus in vitro was used as the bioassay to carry out an activity-directed separation. Bioactive material was concentrated in a 2% acetic acid leaf extract (HOAcE). Potency of HOAcE was increased by the presence of pargyline in the bathing solution. HOAcE was antagonized noncompetively by 1(1-naphthyl) piperazine (1-NP) and cyproheptadine and antagonized competitively by atropine (ATR). Cumulative concentration-response curves of HOAcE and serotonin (5-HT) did not show significant departure from parallelism (P > 0.1) and 5-HT potency was 6040 times that of HOAcE (95% confidence limits: 4620-7850). Solvent extraction of HOAcE split the spasmogenic activity of HOAcE into two types: (i) high-efficacy, low-potency, n-butanol-extracted, pargyline- and 1-NP-sensitive, ATR-insensitive activity, and (ii) low-efficacy, high-potency, ethyl acetate-extracted, pargyline-insensitive, ATR- and 1-NP-sensitive activity. HOAcE lacked muscarinic and nicotinic effects on rat jejunum and frog rectus abdominis. Results suggest the presence of more than one spasmogenic compound in the plant.

Constituents of byrsonima crassifolia and their spasmogenic activity

AbstractIn a biological and phytochemical study on the leaves of Byrsonima crassifolia, 22 compounds were isolated and identified from a MeOH extract. Among the isolates were six triterpenes (betulinaldehyde, betulin, betulinic acid, lupeol, oleanolic acid, and ursenaldehyde), two sterols (β-sitosterol and its glucoside), six flavonoids (catechin, epicatechin, guaijaverin, hyperin, quercetin and its 3-0-[6″-galloyl]galactoside), an aromatic ester (methyl gallate), four common amino acids (alanine, aspartic acid, proline, and valine), two non-protein amino acids (pipecolic acid and 5-hydroxypipecolic acid), and a novel sulfonoglycolipid. Biological evaluations showed that five of these compounds (betulin, betulinic acid, hyperin, quercetin, and ursenaldehyde) exhibited spasmogenic activity on isolated rat fundus, and three isolates (hyperin, pipecolic acid and 5-hydroxypipecolic acid) showed noncompetitive antagonism to serotonin (5-HT) on the same preparation.

Heimia salicifolia : a phytochemical and phytopharmacologic review

Heimia salicifolia grows wild from Mexico to Argentina. The aerial parts have a wide folk reputation for antisyphilitic, sudorific, antipyretic, laxative and diuretic activity, and are reported to be useful in preparing post partum baths and to enhance wound healing. Its four most studied alkaloids are vertine, lyfoline, lythrine and nesodine. Structural relationships of the Heimia alkaloids and certain synthetic 4-arylquinolizidines are reviewed here. Preliminary clinical evaluation indicates that vertine and lythrine given orally appear to lack the psychodysleptic activity that has been touted for native brews said to incorporate H. salicifolia. Most of the animal studies discussed here have focused on the ataractic, antiinflammatory and antispasmodic potential of vertine and on the hydrodiuretic potential of lythrine and decine, a structurally related alkaloid found in Decodon verticillatus. The ataractic activity of vertine does not appear to be dependent on the depletion or blockade of catecholamines, while its antiinflammatory capacity seen in both exudative and immunologic systems seems to be dependent in part on an intact pituitary-adrenal system and in part on inhibition of prostaglandin synthase. The antisplasmodic activity of vertine has been demonstrated on many isolated tissues using different agonists, but appears to be largely musculotropic in nature. Only lythrine and decinine have been shown to be true hydrodiuretics and may prove to be useful in treating Addisons disease and general nephrosis. A number of synthetic 4-arylquinolizidines and related compounds appear to possess antiinflammatory potential.

Brucine lethality in mice

Brucine (2,3-dimethoxystrychnidin1 O-one), an alkaloid originally isolated by Pelletier and Caventou in 1819 from the dry ripe seeds of Strychnos nux-vomica L. (Loganiaceae), has long been characterized as strychnine-like in regard to its pharmacologic and toxicologic effects but less potent than strychnine (Sax and Lewis, 1989). Mays (1887) was the first to demonstrate that there were pharmacologic differences between these two alkaloids, with brucine showing a local anesthetic effect on mucous membranes. While the toxicity indices for strychnine in most laboratory animal species are readily available (Sax and Lewis, 1989), comparable figures are generally lacking for brucine. Morrison and Bliss (1932) concluded from subcutaneous studies of sulfate salts in rabbits, cats and dogs that the potency of brucine was 0.022-0.028 times that of strychnine. In mice, the intravenous ‘toxic’ dose for brucine sulfate was reported to be 33 mg/kg (Wanat, 1931) but this paper did not define the criteria for ‘toxic’ and it is unclear whether the reported figure was for the base or salt. Sandberg and Kristianson (1970), using citrate salts of brucine, reported a subcutaneous LDso in mice for brucine base to be

Prostaglandin synthetase inhibition by alkaloids of Heimia salicifolia

Two alkaloids from Heimia salicifolia, cryogenine and nesodine, were respectively 2.48 and 2.24 times as potent as aspirin as inhibitors of prostaglandin synthetase prepared from bovine seminal vesicles. Reference compounds, indomethacin and phenylbutazone, were respectively 2800 and 8.75 times as potent while a synthetic analogue of cryogenine, JB-1-0, was 0.656 times the potency of aspirin. This activity may help to explain the traditional medicine use of H. salicifolia in the Americas.

Effect of chronic cocaine administration and cocaine withdrawal on coronary flow rate and heart rate responses to epinephrine and cocaine in isolated perfused rat hearts

The acute dose-dependent effects of epinephrine and cocaine on heart rate and coronary flow rate (CFR) were examined in isolated, perfused (Langendorff) rat hearts from animals: i) pretreated with daily cocaine injections (20 mg/kg/day) for 8 weeks; ii) after 2-day withdrawal from 8-week cocaine pretreatment; iii) vehicle-treated controls. Chronic cocaine (CC) hearts were significantly less sensitive to the chronotropic effects of epinephrine than control (C) or withdrawal (CW) hearts. CW hearts exhibited significantly higher heart rates in response to epinephrine than C and CC hearts. Epinephrine alone (2.5 x 10(-7) M) decreased CFR 11% (C), 9%(CC), 14%(CW) from respective baseline levels. Cocaine alone had no significant effect on CFR in C hearts but produced slight dose-dependent decrements in CFR in CC and particularly CW hearts at higher doses. Cocaine plus epinephrine markedly decreased CFR in all groups, particularly in CW hearts. The results indicate that chronic daily cocaine administration produces a functional tolerance of the heart to the chronotropic actions of epinephrine but a 2-day withdrawal from chronic cocaine results in a rebound supersensitivity to adrenergic stimulation and cocaines sympathomimetic effects. In addition, cocaine produces only minor decrements in coronary flow in the rat heart, while cocaine acts synergisticallly with epinephrine to produce a marked decrease in CFR.

Effect of various pretreatments on the hypothermic activity of repin in naive rats

Repin is a sesquiterpene lactone found in Centaurea solstitialis, a plant responsible for Parkinson-like disease in horses. Repin, on intraperitoneal (i.p.) injection, produces a dose-dependent and highly significant hypothermia in naive rats. The hypothermia is long-lasting with a peak 3 h after the injection and a return to normal temperature after more than 8 h. The effects of atropine sulfate, atropine methylbromide, propranolol, metergoline, ketanserin, diphenhydramine and apomorphine pretreatment on repin-induced hypothermia were investigated. None of the pretreatments directly antagonized repins hypothermic effect. However, partial but significant reversals of hypothermia by atropine sulfate, metergoline, ketanserin, diphenhydramine and apomorphine were observed 2-4 h after the repin injection. These late-onset effects are probably due to secondary physiological mechanisms. On the other hand, propranolol, at 20 mg/kg i.p., clearly accentuated both the early-onset (30-90 min) and late-onset (2-4 h) hypothermic effects of repin.

Effects of benzoquinolizine homologues on proliferative and exudative inflammation.

Abstract Cryogenine and a series of ataractic agents inhibit both cotton pellet-induced granuloma formation and carrageenin-induced pedal edema in the rat. Chlorpromazine, reserpine, and one group of benzoquinolizine derivatives (tetrabenazine, benzquinamide, and 2-ethyl-2,3,4,6,7,11b-hexahydro-2-hydroxy-3-isobutyl-9,10-dimethoxy-1H-benzo[h]quinolizine) inhibited inflammation concomitant with but not dependent upon apparent endogenous steroid release. A second type of benzoquinolizine (3-ethyl-2,3,4,6,7,11b-hexahydro-2-hydroxy-2-isobutyl-9,10-dimethoxy-1H-benzo [h]quinolizine) decreased the inflammatory response without apparent adrenal stimulation. Cryogenine was qualitatively different from the other compounds as it appeared dependent upon an intact pituitary-adrenal axis for anti-inflammatory effectiveness.

Inhibitory Effect of 5-Hydroxytryptamine on Rat Stomach Fundus: Mediated Indirectly by Activation of Noradrenaline Release

Biphasic cumulative concentration‐response curves to 5‐hydroxytryptamine (5‐HT) and α‐methyl‐5‐hydroxytryptamine (α‐Me‐5‐HT) using rat stomach fundus in the presence of 50 μm pargyline suggested two sites of interaction (high and low affinity).