Joseph I. Okogun

Preliminary organic geochemical studies of samples from the Niger delta (Nigeria) I. Analyses of crude oils for triterpanes

Abstract Crude-oil samples from three oilfields in the east and west of the Tertiary Niger delta, Nigeria, were analysed for pentacyclic triterpanes by gas chromatography and gas chromatography—mass spectrometry. Previously identified pentacyclanes such as 18αH-oleanane; 1(10→5)-abeo-3β-methyl-24β-nor-25α-18αH-oleanane (spirotriterpane); 30-nor-17αH,21βH-hopane; 17αH,21βH-hopane and 22,29,30-trisnor-18αH-hopane-II were recognised in the crudes. In addition, 17βH,21αH-hopane (moretane) and 17βH,21αH-homohopane (homomoretane) were identified for the first time. Results obtained in the present study indicate that the Nigerian petroleum pentacyclanes belong to at least three homologous series, namely, the 17αH,-21βH-hopanes (αβ); 17βH,21αH-hopanes (βα) and a novel “ K 1 ” series distinguished by members with retention times that were considerably shorter than those of the corresponding αβ hopanes with the same number of C atoms. Mass-spectral and retention-time characteristics of the “ K 1 ” triterpanes classified them neither as the 17αH-hopanes (αα hopane series) nor the recently-discovered methylhopane series. The preponderant pentacyclic triterpanes in the oils sampled from either side of the delta were the αβ hopanes and oleananes. However, the triterpane fingerprint of the western crudes differed significantly from that of their eastern counterparts in the distribution of the oleananes. The relatively higher concentration of the oleananes in the eastern oils apparently reflects a greater input of higher plants to their source sediments, presumably the shale of the paralic Agbada Formation. The relatively lower concentration of the oleananes in the western oils resulted in a dominantly hopane fingerprint, expected for petroleum generated in mainly non-terrigenous source rocks. Therefore, it would appear that the concentration of oleananes in Nigerian petroleum is sufficiently variable with source facies to permit dependable oil—source rock correlation based on triterpane finger-printing.

Preliminary organic geochemical studies of samples from the niger delta (Nigeria): II. Analyses of shale for triterpenoid derivatives

Abstract Immature shale of the Agbada Formation of the Tertiary Niger delta, Nigeria, cored at various depths A simulation experiment carried out by heating the immature shale at 300°C in vacuo (0.4 Torr) for ten days resulted in a triterpane composition similar to that of the delta oils. The disappearance of olean-13 (18)-ene and the generation of oleananes had apparently occurred simultaneously with reported structural changes in the hopane components. The presence of the triterpene in immature shale and its apparent transformation to 18αH-oleanane by in vitro thermal alteration was consistent with the current hypothesis of the origin of oleananes in Nigerian petroleum.

Antiinflammatory and Antimicrobial Activities of Mitracarpus scaber Extracts

AbstractPreliminary investigations were carried out on leaf extracts of Mitracarpus scaber with the goal of establishing its acclaimed potency as an antiinflammatory and antimicrobial agent. Petroleum-ether and methanol extracts were studied. In rats, the extracts progressively reduced fresh egg albuminin-induced edema of the hind paw. There was a dose-related and sustained inhibition of increase in paw circumference caused by subplantar injection of the phlogistic agent. The petroleum ether extract showed a more pronounced effect. In vitro, the extracts caused marked inhibition against some strains of laboratory microorganisms, the order of sensitivity being Pseudomonas aeruginosa> Kleb-sialla pneumoniao>Staphylococcus aureus> Escherichia coli. The extracts also inhibited the growth of Candida albicans. These results help to explain the rationale for the folkloric use of the plant in treating inflammatory disorders and microbial infections.

Roseadione, a diterpene ketone from Hypoestes rosea

Abstract A tricyclic diterpene ketone, roseadione, has been isolated from Hypoestes rosea and its structure established as a dicyclopenta[ a , d ]cyclo

C24–C27 Degraded Triterpanes in Nigerian Petroleum: Novel Molecular Markers of Source/Input or Organic Maturation?

ABSTRACT Ekweozor, CM., Okogun, J.I., Ekong, D.E.U. and Maxwell, J.R., 1981. C 24 –C 27 degraded triterpanes in Nigerian petroleum: Novel molecular markers of source/input or organic maturation? In: A.W. Rose and H. Gundlach (Editors), Geochemical Exploration 1980. J. Geochem. Explor., 15: 653–662. The analyses, by gas chromatography and gas chromatography/mass spectrometry, of the triterpane concentrate of crude oils sampled from various oil fields of the Tertiary Niger delta have revealed the ubiquitous presence of a series of C 24 –C 27 tetracyclic alkanes likely to be novel degraded triterpanes. The presence in the crude oils of a C 25 tricyclic alkane, apparently structurally related to the tetracyclanes, seemed consistent with the hypothesis of sequential cleavages of the terminal rings of precursor pentacyclic triterpenoid derivatives with increasing thermal transformation of the respective petroleums. The degraded triterpanes might be useful for assessing the stages of thermal evolution of petroleum in the reservoir. A possible application, to oil exploration, of the expected variations in the concentration of the polycyclanes in crude oils with different thermal histories would be in distinguishing primary (immature) oils from mature but bio degraded oils.

Myrianthic acid: a triterpene acid from the rootwood of Myrianthus arboreus

Abstract Arjunolic acid and a new triterpene acid, myrianthic acid, were isolated from the rootwood of Myrianthus arboreus . The structures of the two compounds were elucidated by IR, 1 H NMR and mass spectroscopy.

Spectral studies on coumarins and the determination of the constitution of ekersenin by total synthesis

Abstract During the determination of the constitution of ekersenin isolated from Ekererbegia senegalensis , eight isomeric monomethoxy-monomethylcoumarins were synthesised. These studies proved that ekersenin was 4-methoxy-5-methylcoumarin, a constitution with novel biosynthetic implications. Apparently ekersenin is the first example of natural coumarin biosynthesis involving only the polyketide route. Comparative spectral correlations on substituted coumarins are summarised.

Extracts from the fruits of Piper guineense schum. and thonn

Extraction of the fruits of P. guineense with petroleum has yielded the isobutylamides of 13-(3,4-methylenedioxy-phenyl)-2,4,12-tridecatrienoic, 13-(3,4-methylenedioxyphenyl)undeca-2,4,12-trienoic, eicosa-2,4-dienoic, octadeca-2,4-dienoic, and hexadeca-2,4-dienoic acids, as well as the known amides piperine, trichostachine, and piperlonguminine, and a mixture of unidentified sterols.

Effect of oral administration of aqueous whole extract of cassytha filiformis on haematograms and plasma biochemical parameters in rats.

IntroductionWe evaluated the sub-chronic toxicity of the aqueous herbal extract prepared fromCassytha filiformis and administered daily for 28 days at dose levels (250, 500, and 1000 mg/kg bw) in male wistar albino rats. The LD50 of the aqueous extract was determined.MethodsThe effects on body weights, organ weights, and certain haematological and plasma biochemical parameters were measured as indices of organ toxicity.ResultsThe aqueous extract did not affect plasma glutamate oxaloacetate transaminase (GOT) and glutamate pyruvate transaminase (GPT); however, a significant reduction in alkaline phosphatase (ALP) level occurred in all the treated groups. It also did not affect the electrolytes (Na+, Cl− and K+), total and direct bilirubin, creatinine, and glucose level. The aqueous extract elicited hypercholesterolaemic effects, but it did not affect the Hb, WBC, RBC, PVC, platelets, MCH, MCHC, MCV levels and differential counts (lympocytes, neutrophils, monocytes, eosinophils and basophils). It also reduced the body weight gain and absolute weight of the kidneys. The relative weights of the heart and lungs in some animal groups were equally reduced. The acute toxicological evaluation of the plant extract revealed an oral LD50 value greater than 500 mg/kg bw.ConclusionThis study suggests that aqueous extract ofC. filiformis administered at normal therapeutic doses is not likely to produce severe toxic effects on some organs or haematological and biochemical indices in rats.

Revised structure and synthesis of piperolein acids, guineensine and wisanine from Piper guineense

Abstract The structures of piperolein acids guineensine and wisanine have been confirmed by synthesis, UV irradiation of trans piperolein B acid ester gave the cis-isomer reported in the literature as the trans-isomer. The trans-2, trans-4 ethylenic bonds in guineensine and wisanine were introduced by reacting piperolein B aldehyde and 2-methoxy piperonal with the appropriate Wittig or Reformatsky reagent.