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A review of the geographical distribution, clinical use, biological activity and phytochemistry of Oldenlandia affinis (R&S) DC. is presented. During an inventory of medicinal plants in northern Congo/Brazzaville and south-western Central African Republic in 1962, 196 different species were registered, one of which was O. affinis used for the facilitation of childbirth. A medical team working in Luluabourg (Kananga) in Congo during the troubled period in 1960, discovered also the traditional use of the same plant as an oxitocic agent during labour. The plant was collected and the uterotonic substances isolated. Cyclic peptides (called Kalata-peptides) were described, and the main peptide, B1, was subjected to pharmacological and chemical investigations. Later the three-dimensional structure of the peptide was determined. Similar cyclic peptides have been isolated also from other plants in the Rubiaceae family like Chassalia pasvifoloia and Psychotria longipes, and from Viola species: Viola tricolor L. and Viola arvensis Murray. Some of these peptides, included Kalata-peptide B1, have been shown to hold antimicrobial activity. They have recently been synthesized, and they may represent a starting point for the design of new peptide antibiotics.

A collection of 32 botanically identified medicinal plants from the slopes of Mt. Cameroon made by two Swedish settlers in the beginning of the last century is described and the literature is followed up. The drug names were found to be unaltered during the century passed.

Four triterpenoid saponins isolated from the stem bark of Lecaniodiscus cupanioides and denoted S-2,S-3,S-4 and S-5, were identified as follows. S-2:3-O-[α- l -arabinopyranosyl-(1→3)-α- l -rhamnopyranosyl-(1→2)-α- l -arabinopyranosyl]-hederagenin; S-3:3-O-[α- d -xylopyranosyl-(1→3)-α- l -rhamnopyranosyl-(1→2)-α- l -arabino-pyranosyl ]-hederagenin; S-4:3-O- [α- l -arabinopyranosyl-(1→3)-α- l -rhamnopyranosyl-(1→ 2)-α- l -arabinopyranosyl]-hederagenin; S-5:3-O- [α- l -rhamnopyranosyl-(1→2)-α- l -arabinopyranosyl ]-hederagenin. Of these, S-2 and S-4 are new substances.

During chemical investigation for compounds possessing biological activity in the stem and rootbark of Tabernaemontana dichotoma, 22 alkaloids were isolated. Ten monomeric alkaloids were identified, viz. (−)-apparicine, coronaridine, 3-oxocoronaridine, 3-ketopropylcoronaridine, 19R-heyneanine, 3-ketopropyl-19R-heyneanine, ibogamine, isomethuenine, perivine and vobasine. Two of the monomeric alkaloids isolated were new, one was identified as 3,19R-oxidocoronaridine and the other one is not yet identified. The other ten alkaloids isolated were dimeric compounds, three were identified as tabernamine, voacamine and 3′R/S-hydroxyvoacamine. Five of the dimers were new alkaloids related to tabernamine and ervahanine type structures and identified as 3′R/S-hydroxytabernamine, 3′R/S-hydroxy-N4-demethyltabernamine, N4-demethyltabernamine and 3′R/S-hydroxy-N4-demethytervahanine A and B. The remaining two alkaloids are partially characterized.

Δ1-Tetrahydrocannabinol (Δ1-THC) administered i.v. (1 mg/kg) to anaesthetized rats with cannulated bile ducts is rapidly eliminated as metabolites in the bile. 60–70 per cent in 6 hr. In comparison with the slow excretion via faeces an extensive enterohepatic circulation, which may be of toxicological importance, is indicated. Unchanged Δ1-THC and cannabinol are eliminated in low amounts (0.05 0.1 percent) in the bile. A few per cent consists of two or more mono-oxygenated metabolites. neither of which is identical with 7-hydroxy-Δ1-THC or 6-β-hydroxy-Δ1-THC. The main part of the non-conjugated metabolites is present as compounds more polar than 7-hydroxy-Δ1-THC and as carboxylic acids. These acids were more polar than Δ1-THC-7-oic acid which could not be identified in a free or conjugated form. In the rat about 60 per cent of the metabolites are eliminated as water-soluble conjugates. Hydrolysis with glucuronidase liberated aglycones which were mainly neutral whereas hydrolysis with alkali released neutral but also some acidic compounds. 7-Hydroxy-Δ1-THC was identified as an aglycone of glucuronic acid and furthermore, three mono-oxygenated cannabinoids were isolated after hydrolysis and partially characterized.

Δ1-Tetrahydrocannabinol-3H is almost completely metabolized to more polar metabolites after intravenous (i.v.) injection in the rabbit. About 35 per cent of the dose is excreted in the urine during the first 24 hr as compared to only 10 per cent in the faeces. A considerable amount (4–10 per cent) of the radioactivity excreted in the 24-hr urine is extractable with ether and upon acidification of the urine the extractable amount increases four times or more. At least three major metabolites of Δ1-THC-3H are excreted in the urine. The half-life of radioactivity in blood after i.v. injection of Δ1-tetrahydrocannabinol-3H ranged from 7 to 16 min. The compound is rapidly metabolized and 30 min after i.v. administration of †1-tetrahydrocannabinol-3H, only 3–4 per cent of the radioactivity in the blood is due to unchanged compound. The blood level of an ether-soluble metabolite reaches its maximum 0.5–2 hr after injection. Thus, the formation of a pharmacologically active metabolite cannot be excluded at present. The distribution of radioactivity in tissues largely reflect the elimination of Δ1-tetrahydrocannabinol-3H through liver and kidneys. Brain and spinal cord show the lowest activity levels of all the investigated tissues. Three days after administration high levels of radioactivity still persist in body fat and spleen.

The pharmacological approach to the study of plants used in traditional medicine is discussed. On the basis of personal experience in the Republics of Congo and Central Africa the author finds only a very small percentage of non-active plants among those used in traditional medicine. Some previously unknown plants are reported.

From the seeds of TABERNAEMONTANA DICHOTOMA, the alkaloids coronaridine, ibogamine, stemmadenine, tabersonine, voacangine, voaphylline and voaphylline hydroxyindolenine were isolated and identified. The crude seed extract showed spasmolytic activity.

Stemmadenine, the major alkaloid from the seeds of Tabernaemotana dichotoma , showed hypotensive activity and weak muscle relaxant activity. Perivine, vobasine, coronaridine and dichomine, some of the alkaloids found in the leaves, fruits and bark of T. dichotoma , also showed hypotensive and muscle relaxant activity.

The binding of tritium-labelled Δ1-tetrahydrocannabinol to human plasma proteins in vitro was studied with electrophoretic techniques. Δ1-Tetrahydrocannabinol was found to be associated to 80–95 per cent with lipoproteins.

A method is described for the preparation of tritium-labelled Δ9-tetrahydrocannabinol and other cannabinols. Intravenously injected Δ9-tetrahydrocannabinol-H3 is eliminated very slowly by the rat; half of the administered dose still remained in the body after one week. About 80 per cent of the drug is excreted in metabolized form via faeces, the remainder being eliminated also as metabolites in the urine. During the first 24 hr 2–6 per cent of the injected activity appears in the urine, but less than 0.006 per cent of the dose, if any, is excreted unchanged. A considerable amount of the activity is readily extractable with ether and possibly an identification method for Cannabis-users may be based on the occurrence of this metabolite. Δ9-Tetrahydrocannabinol is apparently not excreted as a glucuronide.

A method to identify and accurately measure non-labelled Δ1-tetrahydrocannabinol (Δ1-THC) in blood of cannabis smokers has been developed. It consists of the following steps: To a 5 ml plasma sample is added deuterated Δ1-THC (Δ1-THC-d2) as internal standard. After extraction with light petroleum and evaporation, the Δ1-THC containing fraction is separated by chromatography on Sephadex LH-20 (1 times 40 cm) using light petroleum-chloroform-ethanol (10:10:1) as eluant. A fraction containing Δ1-THC is collected and subjected to mass fragmentography (LKB 9000; 3% OV-17/Gas-Chrom Q; 230°). The mass spectrometer was adjusted to record the intensities of m/e 299 and 314 of Δ1-THC and m/e 301 and 316 of Δ1-THC-d2. The standard curve was made by plotting peak height m/e 299/m/e 301. Peak levels of 19–26 ng ml−1 were reached within 10 min after smoking a cigarette containing 10 mg Δ1-THC.