Phytochemical Profiling of Parquetina Nigrescens Extracts by GC-MS, HPLC and FTIR

Background Parquetina nigrescens is widely used in traditional medicine and has reported normoglycaemic potential. However, the specific active chemical constituents and mechanisms responsible for these effects remain insufficiently clarified, and variability between studies is likely when extracts are not chemically standardised. Systematic chemical profiling using polarity-guided fractionation, chromatographic separation, and marker quantification is therefore essential to define extract composition more reproducibly and provide a credible analytical foundation for subsequent pharmacological and mechanistic investigations. Aim To generate an integrated chemical profile of Parquetina nigrescens extract using polarity-guided solvent fractionation followed by complementary instrumental analyses (GC–MS, HPLC, and ATR-FTIR) in support of extract standardisation and future bioactivity-driven studies. Methods A Parquetina nigrescens extract (6.02 g) obtained from the Department of Pharmacognosy, Faculty of Pharmacy, University of Lagos, Nigeria, was dispersed in methanol (70 mL), distilled water (50 mL), and ethanol (10 mL) to obtain a partitionable mother solution. Sequential solvent–solvent partitioning was performed in triplicate using n-hexane (non-polar), dichloromethane (mid-polar), ethyl acetate (intermediate-polar), and an aqueous residue (polar). The n-hexane fraction was analysed by GC–MS using an Agilent 5977B GC/MSD system with an Elite-5MS column under electron ionisation at 70 eV (helium carrier gas at 1 mL/min; injection 1 µL, split 10:1; oven 100°C for 0.5 min then 20°C/min to 280°C, hold 2.5 min; mass range m/z 45–450). ATR-FTIR spectra of the dichloromethane, ethyl acetate, and aqueous extracts were acquired using an Agilent Cary 630 Diamond ATR accessory. HPLC profiling and quantification were carried out using external calibration with mixed standards under two methods (isocratic and gradient) on a C18 column with UV detection at 257–260 nm; extract (50 mg) was prepared at 10 mg/mL in methanol, filtered (0.45 µm), and injected (10 µL). Results GC–MS of the n-hexane fraction identified eight compounds (retention time 13.50–17.01 min) with a total oil content of 25.3%. The most abundant constituents by percentage composition were 3H-Naphth[1,8a-b]oxiren-2(1aH)-one (6.51%), hexadecanoic acid ethyl ester (5.10%), and ethyl 9,12,15-octadecatrienoate (4.54%). Additional constituents included linoleic acid ethyl ester (2.86%), phenol, 4-[4,5-bis[4-(dimethylamino)phenyl]-4H-imidazol-2-yl]- (2.64%), octadecanoic acid ethyl ester (1.03%), and two sterol/terpenoid-like acetates (0.97–1.65%). HPLC profiling resolved three phytochemicals: quercetin (retention time 1.757 min; peak area 3593.212), magnoflorine (1.248 min; area 841.4059), and rutin (1.558 min; area 724.4042). Interpolated concentrations were quercetin 260.486 µg/mL, magnoflorine 63.03 µg/mL, and rutin 17.45 µg/mL. ATR-FTIR analysis across dichloromethane, ethyl acetate, and aqueous extracts showed bands consistent with O–H stretching (≈ 3369–3280 cm⁻¹), C–H stretching (≈ 2929–2855 cm⁻¹), carbonyl C = O (≈ 1685–1636 cm⁻¹), C–O/C–N stretching (≈ 995–1275 cm⁻¹), aromatic or alkene-associated absorptions (≈ 1603 cm⁻¹), and nitrile C ≡ N features (≈ 1938–2113 cm⁻¹), supporting the presence of diverse chemical classes across fractions. Conclusion Polarity-guided solvent fractionation combined with GC–MS, HPLC, and ATR-FTIR provided a complementary framework for reproducible chemical profiling of Parquetina nigrescens. The non-polar fraction was enriched in fatty acid ethyl esters, while HPLC confirmed quercetin, magnoflorine, and rutin as quantifiable marker constituents. FTIR data further supported broad functional-group diversity consistent with phenolic-, alkaloid-, carbonyl-, nitrile-, and lipid-associated constituents. These findings provide fraction-specific and quantitative chemical evidence that can support standardisation, improve comparability between studies, and guide future isolation and bioactivity or mechanistic investigations.