Bioactive phytochemicals in an aqueous extract of the leaves of Talinum triangulare

Abstract An aqueous leaf extract of Talinum triangulare was screened for the presence of bioactive molecules, using gas chromatography coupled with pulse and flame ionization detectors. It had high carotenoids; moderate benzoic acid derivatives, hydroxycinnamates and flavonoids; and low terpenes, alkaloids, phytosterols, allicins, glycosides, saponins, and lignans contents. Ten known carotenoids (mainly 50.42% carotene and 33.30% lycopene), nine benzoic acid derivatives (mainly 84.63% ferulic acid and 11.92% vanillic acid), and six hydroxycinnamates (55.44% p‐coumaric acid and 44.46% caffeic acid) were detected. Also detected were eight lignans (88.02% retusin) and thirty flavonoids (50.35% quercetin and 39.36% kaempferol). The medicinal properties of the major components of these phytochemical families that were detected in the aqueous extract of the leaves were discussed herein and proposed to be explored for their potential health benefits. The great number of potentially active biomolecules and their multifunctional properties make Talinum triangulare a ready source of health‐promoting substances.


| INTRODUCTION
Talinum triangulare (Jacq.) Willd. (Family: Portulaceae), is commonly called waterleaf. It is an herbaceous, annual, coalescent, and glabrous plant widely grown in tropical regions as a leafy vegetable. In Nigeria, it is consumed as a leafy vegetable and constituent of sauces (or vegetable soups). Nutritionally, it is a good source of some minerals (e.g., calcium, magnesium, and potassium) and vitamins (e.g., ascorbic acid and pyridoxine) (Oguntona, 1998). The extract from the leaves and roots is used to cure asthma (Ogie-Odia & Oluowo, 2009). According to Ofusori et al. (2008), "waterleaf consumption has benefiting effects on the neurons of the cerebrum and may probably enhance the cognitive ability in Swiss albino mice". In Edo State, Nigeria, Talinum triangulare is used as a diuretic, and for the management of gastrointestinal disorders (Mensah, Okoli, Ohaju-Obodo, & Eifediyi, 2008). It is also used to treat Shistosomiasis, scabies, fresh cuts, high blood pressure, and anemia (Ogunlesi et al., 2010).
(2014) did not quantify the detected compounds. To this end, this study profiled and quantified the phytochemical composition of an aqueous extract of the leaves of Talinum triangulare, and in addition discussed the bioactivities of the most abundant of the detected compounds, with a view to highlighting the possibilities of the use of the leaves as a functional food, or as a source of nutraceuticals.

| Collection of plant samples and preparation of aqueous extract
Samples of fresh waterleaf plants were collected from within the Choba They were then rid of dirt and their leaves were removed, oven dried at 55°C, and ground into powder. The powder was soaked in boiled distilled water for 12 hrs, after which the resultant mixture was filtered and the filtrate was evaporated to dryness. The percentage recovery of the crude extract was 2.296%. The residue obtained from the crude aqueous extract was subjected to phytochemical analysis.

| General procedures
Gas chromatography was carried out at Multi-environmental Management Consultants Limited, Igbe Road, Ikorodu, Lagos, with a Hewlett Packard HP 6890, gas chromatograph, fitted with HP Chemstation Rev. A09.01[1206] software, to identify and quantify the compounds. The standards were from Sigma-Aldrich Co. and Lynnchem Biological Technology Co. Standard solutions were prepared in methanol for alkaloids, flavonoids, allicins and benzoic acid derivatives; acetone for carotenoids and lignans; methylene chloride for phytosterols and terpenes; and ethanol for hydroxycinnamates, glycosides and saponins. The linearity of the dependence of response on concentration was verified by regression analysis. Identification was based on comparison of retention times and spectral data with standards. Quantification was performed by establishing the calibration curves for each compound determined, using the standards.

| Determination of phytochemical composition
The flavonoids' extract was obtained in a similar way as was reported  (2015). The lignans' extract was prepared according to the method of Chapman, Knoy, Kindscher, Brown, and Niemann (2006), and subjected to gas chromatography with similar conditions as earlier reported by Ikewuchi, Ikewuchi, and Ifeanacho (2014). The benzoic acid derivatives' extract was prepared according to the method of Ndoumou, Ndzomo, and Djocgoue (1996), before being subjected to gas chromatography, with similar conditions as earlier reported by Ikewuchi et al. (2014).
The alkaloids' extract was prepared according to the method of Tram, Mitova, Bankova, Handjieva, and Popov (2002), and subjected to gas chromatographic analysis, with conditions as earlier reported by Ikewuchi et al. (2014). The carotenoids' extract was prepared according to the method of Rodriguez-Amaya and Kimura (2004) (2007), and subjected to gas chromatography, with similar conditions as earlier reported by Ikewuchi, Ikewuchi, Ifeanacho, Igboh, and Ijeh (2013). The allicins' extraction was carried out in a similar way as reported by Roy, Shakleya, Callery, and Thomas (2006); and the resultant extract was subjected to gas chromatography with similar conditions as was earlier reported by Ikewuchi et al. (2013). The saponins' extraction was carried out in a similar manner as the one reported by Guo, Zhang, and Liu (2009). The extract obtained was subjected to gas chromatography with similar conditions as was earlier reported by Ikewuchi et al. (2013). The terpenes' extraction was carried out in a similar way as reported by Ortan et al. (2009). The resultant extract was subjected to gas chromatography, with similar conditions as was earlier reported by Ikewuchi et al. (2013).

CONFLICT OF INTEREST
We declare that we have no conflict of interest. Values are mean ± SD (standard deviation) of duplicate determinations.