Department of Pharmacy, University of Nigeria, Nsukkn, Nigeria
ESSENTIAL OILS OF NIGERIA Part 111. Essential Oil of Dennettia
The fruits Dennettia tripetala G . BAKER(Annonaceae) yielded 3.6-4.0% o f essential oil containing about 25% o f fi-phenyl-nitroethane. Some physical constants were determined for the oil, and distinguishing characters found between Dennettia fruits and those o f the very similar Uvaria chamae P. B ~ ~ u v . ( A n n o n a ceae).
In the first two parts of this series of investigations, the essential oils of Eucalyptus and Fennel were dealt with ( O s r s r o ~ u 1966 , and 1967). Dennettia tripetala G . BAKERis a shrub commonly found in the southern parts of Nigeria. Its fruits are much cherished for their fragrance and pungency, and are eaten, ripe o r unripe either alone o r as an adjuvant to cola nuts or the garden egg (Solanum incanum LINN).T h e pungent principle resides in the seeds, and not in the pericarp o r fruit pulp both of which become sugary when the fruit ripens. The plant produces the fruits seasonally (between April and June), but there is no evidence that it has been put into any serious commercial cultivation. In offseason periods the fruits may be found on the markets in the dried form, having been dried in the sun o r over wood fires. OKOGUN and EKONG(1969) extracted the fresh fruits with petroleum spirit and identified the pungent and fragrant principle as fi-phenyl-nitroethane. They also obtained a sesquiterpene hydrocarbon mixture whose infrared spectrum showed no O H or C O group, and which they did not investigate further. As can be observed in the Plate (A), the fruits of Dennettia are oblong o r cylindrical with parallel impressions of the seeds on the fruit wall. These seed impressions are most strongly marked in the dried fruits. The fruits measure 0.50-1.91-4.00 cm in lenght, and 0.40-0.92-1.50 cm in width. Also in the Plate (B) are the fruits of Uvaria chamae P. BEAUV.which are similar in appearance and comparable in dimensions to those of Dennettia. However, the seed impresslions in Uvaria are less marked, and the pericarp more brown than in Dennettia. Although the fruits of Uvaria have a slight flavour reminiscent of that of Den-
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Abstract
288
Osisiogu
Planta medica Vol. 27 1975
'
Figure 1. A: Fruits of Dennettia tripetala G. BAKER B: Fruits of Uvaria chamae P. BEAUV.
Magnification X 0.47
Materials and Methods T h e fruits of Denrrettia and Uvaria were dried in the sun, coarsely powdered and steamdistilled. The isolatad Dennettia oil was dried over anhydrous sodium sulphate and some of its physical constants obtained as shown below. An infrared spectrum of a film of the oil was run. T h e oil was examined by thin layer chromatography (TLC) using silica gel layers, and chloroforrn/benzene (1 : 1) as solvent. T o detect the terpenes the fluoresceinlbrornine reaction was carrieaout (Randerath, 1964). The plates were also exposed to iodine vapours. An estimate of the proportion of P-phenyl-nitroethane in the oil was made by subjecting the 1967) and weighing the benzoic acid resulting oil to alkaline perrnanganate oxidation (OS~SIOGU, from the f3-phenyl-nitroethane. Finally, a microscopic examination of the powders of Dennettia and Uvaria fruits was carried out.
Results and Discussion Dennettia fruits yielded 3.6-4.0% of a fragrant deep yellow oil with a sweetish and pungent taste. T h e following physical properties were established:
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nettia they are not pungent, and when ripe, the sugary fruit pulp is sucked and the seeds and pericarp are discarded. Since the pleasant aroma of the fruits of Dennettia recommends them as a ~ o s s i b l efood flavour, this investigation has been undertaken t o isolate the essential oil and t o examine some of its properties. An examination has also been carried out o n the fruits of Uvaria which constitute a potential adulterant of Dennettia fruits with a view to establishing any important distinguishing characters between the two fruits, especially in the powdered form.
289
Weight per mil: 1.068; Refractive index: 1.5150; Optical rotation (at 25" C):-0.8 Solubility in alcohol: Clearly soluble in 5 to 5.5 volumes of 80% alcohol and more, up to 10 volumes Congealing point: did not congeal a t - 5' C From the above i t can be seen that the oil is slightly heavier than water, and that it contains little or no crystalline material since it did not congeal even when cooled down t o -So C: T h e infrared spectrum showed no absorption bands for OH o r CO, thus indicating the absence of oxygenated compounds in the oil, but bands were observed at 1382cm-I (-NOs); 1610,1502,1460, and 1437cm-I (aromatic nucleus); and 755, 703 cml (monosubstituted benzene ring). These results confirm the presence of P-phenyl-nitroethane earlier characterised in the fruit extracts (OKOGUNand EKONG,1969) in the oil. The T L C examination showed five unidentified terpene components with Rf values, 0.06, 0.34, 0.40, 0.65 and 0.76 respectively. Treatment of 1g of the oil with alkaline permanganate yielded 0.206 g (average of three determinations) of benzoic acid (m. p. 122' C). Theoretically this is equivalent to 0.255 g of p-phenyl-nitroethane. Therefore' the oil contains about 25% of the nitro compound. T h e fruits of Uvaria did not yield an essential oil when distilled. By microscopic examination, it was found that the fibres of Dennettia and Uvaria were identical in form but that those of Uvaria were lignified whereas those of Dennettia were not. These observations are therefore of diagnostic value.
Conclusion Dennetia fruits yield a relatively high amount of essential oil containing about 25% of S-phenyl-nitroethane. It has been reported that varying quantities of Dennettia fruits when eaten induce diarrhoea (OKOGUN and EKONG,1969), but the principle causing this appears t o be unknown, and it is not certain whether the isolated essential oil would have the same effect. However, used in small quantites, Dennetia oil has some potentiaI as a flavour for foods, drinks o r medicinal preparations. References OKOCUN, J. I., and EKONG, D. E. U.: Chemistry and Industry, 6 September, 1772 (1969) O s ~ s ~ o c I.u ,U. W.:West African Pharmacist 8, 8 (1966) Os~srocu,I. U. W.:Planta Medica 15,30 (1967) Address: Dr. I. U..W . Osisiogu, Faculty of Biological Sciences, Department of Pharmac3: University of Nigeria, Nsukka, Nigeria
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Essential Oil of Dennettia
ESSENTIAL OILS OF NIGERIA Part 111. Essential Oil of Dennettia
The fruits Dennettia tripetala G . BAKER(Annonaceae) yielded 3.6-4.0% o f essential oil containing about 25% o f fi-phenyl-nitroethane. Some physical constants were determined for the oil, and distinguishing characters found between Dennettia fruits and those o f the very similar Uvaria chamae P. B ~ ~ u v . ( A n n o n a ceae).
In the first two parts of this series of investigations, the essential oils of Eucalyptus and Fennel were dealt with ( O s r s r o ~ u 1966 , and 1967). Dennettia tripetala G . BAKERis a shrub commonly found in the southern parts of Nigeria. Its fruits are much cherished for their fragrance and pungency, and are eaten, ripe o r unripe either alone o r as an adjuvant to cola nuts or the garden egg (Solanum incanum LINN).T h e pungent principle resides in the seeds, and not in the pericarp o r fruit pulp both of which become sugary when the fruit ripens. The plant produces the fruits seasonally (between April and June), but there is no evidence that it has been put into any serious commercial cultivation. In offseason periods the fruits may be found on the markets in the dried form, having been dried in the sun o r over wood fires. OKOGUN and EKONG(1969) extracted the fresh fruits with petroleum spirit and identified the pungent and fragrant principle as fi-phenyl-nitroethane. They also obtained a sesquiterpene hydrocarbon mixture whose infrared spectrum showed no O H or C O group, and which they did not investigate further. As can be observed in the Plate (A), the fruits of Dennettia are oblong o r cylindrical with parallel impressions of the seeds on the fruit wall. These seed impressions are most strongly marked in the dried fruits. The fruits measure 0.50-1.91-4.00 cm in lenght, and 0.40-0.92-1.50 cm in width. Also in the Plate (B) are the fruits of Uvaria chamae P. BEAUV.which are similar in appearance and comparable in dimensions to those of Dennettia. However, the seed impresslions in Uvaria are less marked, and the pericarp more brown than in Dennettia. Although the fruits of Uvaria have a slight flavour reminiscent of that of Den-
Downloaded by: National University of Singapore. Copyrighted material.
Abstract
288
Osisiogu
Planta medica Vol. 27 1975
'
Figure 1. A: Fruits of Dennettia tripetala G. BAKER B: Fruits of Uvaria chamae P. BEAUV.
Magnification X 0.47
Materials and Methods T h e fruits of Denrrettia and Uvaria were dried in the sun, coarsely powdered and steamdistilled. The isolatad Dennettia oil was dried over anhydrous sodium sulphate and some of its physical constants obtained as shown below. An infrared spectrum of a film of the oil was run. T h e oil was examined by thin layer chromatography (TLC) using silica gel layers, and chloroforrn/benzene (1 : 1) as solvent. T o detect the terpenes the fluoresceinlbrornine reaction was carrieaout (Randerath, 1964). The plates were also exposed to iodine vapours. An estimate of the proportion of P-phenyl-nitroethane in the oil was made by subjecting the 1967) and weighing the benzoic acid resulting oil to alkaline perrnanganate oxidation (OS~SIOGU, from the f3-phenyl-nitroethane. Finally, a microscopic examination of the powders of Dennettia and Uvaria fruits was carried out.
Results and Discussion Dennettia fruits yielded 3.6-4.0% of a fragrant deep yellow oil with a sweetish and pungent taste. T h e following physical properties were established:
Downloaded by: National University of Singapore. Copyrighted material.
nettia they are not pungent, and when ripe, the sugary fruit pulp is sucked and the seeds and pericarp are discarded. Since the pleasant aroma of the fruits of Dennettia recommends them as a ~ o s s i b l efood flavour, this investigation has been undertaken t o isolate the essential oil and t o examine some of its properties. An examination has also been carried out o n the fruits of Uvaria which constitute a potential adulterant of Dennettia fruits with a view to establishing any important distinguishing characters between the two fruits, especially in the powdered form.
289
Weight per mil: 1.068; Refractive index: 1.5150; Optical rotation (at 25" C):-0.8 Solubility in alcohol: Clearly soluble in 5 to 5.5 volumes of 80% alcohol and more, up to 10 volumes Congealing point: did not congeal a t - 5' C From the above i t can be seen that the oil is slightly heavier than water, and that it contains little or no crystalline material since it did not congeal even when cooled down t o -So C: T h e infrared spectrum showed no absorption bands for OH o r CO, thus indicating the absence of oxygenated compounds in the oil, but bands were observed at 1382cm-I (-NOs); 1610,1502,1460, and 1437cm-I (aromatic nucleus); and 755, 703 cml (monosubstituted benzene ring). These results confirm the presence of P-phenyl-nitroethane earlier characterised in the fruit extracts (OKOGUNand EKONG,1969) in the oil. The T L C examination showed five unidentified terpene components with Rf values, 0.06, 0.34, 0.40, 0.65 and 0.76 respectively. Treatment of 1g of the oil with alkaline permanganate yielded 0.206 g (average of three determinations) of benzoic acid (m. p. 122' C). Theoretically this is equivalent to 0.255 g of p-phenyl-nitroethane. Therefore' the oil contains about 25% of the nitro compound. T h e fruits of Uvaria did not yield an essential oil when distilled. By microscopic examination, it was found that the fibres of Dennettia and Uvaria were identical in form but that those of Uvaria were lignified whereas those of Dennettia were not. These observations are therefore of diagnostic value.
Conclusion Dennetia fruits yield a relatively high amount of essential oil containing about 25% of S-phenyl-nitroethane. It has been reported that varying quantities of Dennettia fruits when eaten induce diarrhoea (OKOGUN and EKONG,1969), but the principle causing this appears t o be unknown, and it is not certain whether the isolated essential oil would have the same effect. However, used in small quantites, Dennetia oil has some potentiaI as a flavour for foods, drinks o r medicinal preparations. References OKOCUN, J. I., and EKONG, D. E. U.: Chemistry and Industry, 6 September, 1772 (1969) O s ~ s ~ o c I.u ,U. W.:West African Pharmacist 8, 8 (1966) Os~srocu,I. U. W.:Planta Medica 15,30 (1967) Address: Dr. I. U..W . Osisiogu, Faculty of Biological Sciences, Department of Pharmac3: University of Nigeria, Nsukka, Nigeria
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Essential Oil of Dennettia
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