Abstract

A study of the Phytochemical, Nutritional, Pharmacological and Toxicological

Properties of Some Plant Species in a Tropical Rainforest in Akwa Ibom State,

Nigeria was designed to assess eight plant species for some properties that might

explain their floral characteristics and values to humans. Plant samples were

collected from Stubbs Creek Forest Reserve in Akwa Ibom State, Nigeria. Plant

parts collected were seeds or fruits and stem bark. Fruits were processed manually

to obtain their seeds. Proximate screening of seeds and stem bark showed

significant disparities among the plant species in such contents as percentage crude

protein, dry' matter, ash, moisture, fat and carbohydrate. The disparities were

observed not only among plant species but also within some plant families. For

instance, within the family Guttiferae, Garcinia kola seeds contained 14.595950%

crude fibre while Allanblackia floribuanda seeds contained as low as 3.992464%

crude fibre. Also, Garcinia kola seed contained only 2.144662% fat while

Allanblackia floribunda seeds had as much as 58.689749% fat content. The high fat

content of Allanblackia floribunda seeds as well as those of Poga oleosa seeds

(67.964640%) and Irvingia gabonensis seeds (51.507800%) reflected their lipid

status and therefore the oil-producing potential of these species. It is stressed in this

study that apart from the provision of food and shelter, forest plants are important

sources of useful phytochemicals. Phytochemical analysis done revealed the

presence of bioactive compounds such as flavonoid, saponin and phenol which w ere

all in very' low concentrations. Alkaloid presence was relatively in moderate

concentrations. Medicinal values of plants to humans have been strongly

demonstrated in such species as Mangifera indica, Garcinia kola and Dennettia

tripetala. Mineral analysis showed notable variations among the plant species. Low

concentrations or total absence of heavy metals in seeds such as Garcinia kola, Poga

oleosa and Dennettia tripetala make them safer as masticatories in human use. The

carbohydrate contents of these seeds were also very high which showed their

energy-giving property. For the two plant species styled “ordeal plants”

{Physostigma venenosum and Erythrophleum ivorense), tests with albino mice

proved their toxicological properties. For Physostigma venenosum seeds, LD$o

calculated was 1.697 mg/kg which proved lethality of the seeds even at low

concentrations. For Erythrophleum ivorense bark, LD<o calculated was 489.90

mg/kg which showed the species as only lethal in high concentrations. The strong

evidence of toxicity debunks the idea of either species being a supernatural lie

detector, for which reason awareness campaign is recommended to bring any

community still using either species for trial-by-ordcal to quit the practice.