Figure C 4: GC-MS Chromatogram for 1,2-Benzenedicarboxylic acid, butyl 2-methylpropyl ester (1,2BAB-2-MPE)
Figure C 3 and Supplementary Table S9, presents, GC-MS fragmentation analysis of Geraniin (98% w/w), revealed 20 compounds with 1,2-Benzenedicarboxylic acid, butyl 2-methylpropyl ester (1,2BAB-2-MPE) (18.509%), Phytol, acetate (16.05%) and 3,7,11,15-Tetramethyl-2-hexadecen-1-ol (12.46%) as the compounds with the highest compositions. The compound 3,7,11,15-Tetramethyl-2-hexadecen-1-ol have also been identified in methanolic leaf extracts of the Annona muricata and reported to possess cancer-preventive, antimicrobial, anti-inflammatory anti-diuretic and anti-oxidant properties (Shibula and Velavan, 2015). The antiviral compound, 1,2-Benzenedicarboxylic acid, butyl 2-methylpropyl ester (1,2BAB-2-MPE) as presented in Figure C 4 below, is reported for the first time as a fragment of Geraniin.
Phytol, acyclic diterpene alcohol was identified as one of the compounds in Geraniin fragments ethanolic crude (SME), SMEH, SMEDCM, SMMH and SMMDCM . Phytol was previously reported by other researchers to exhibit anti-cancer, anti-microbial and anti-oxidant activities (Cos et al., 2006, Costa et al., 2012a, Costa et al., 2012b, Silva et al., 2014) and could be responsible for synergistic pharmacological action of these extracts. Phytol has been reported to be identified in hydroethanolic extracts ofAbutilon indicum used in the Indian system of medicine (Thakor et al., 2016). Therefore the identification of phytol in the ethanolic extracts is in line with our findings.
Table S 10, presents a similarity table of compounds identified in GC-MS analysis of Geraniin and fractionated alcoholic leaf extracts ofS. mombin . In the comparative GC-MS analysis of SM leaf extracts and Geraniin fragments, as presented in Table S 10, similar compounds such as 1-Tetradecene and n-Nonadecanol-1 found in Geraniin were also identified in all fractionated alcoholic leaf extracts. As previously established in the background literature, Geraniin, found inS mombin and other extracts from the plant is known to have several pharmacological activities. This underscores the pharmacological potential of the plant and its compounds. Fragmentation of large molecules to smaller and simpler compounds could increase the drug-likeness, bioactivity, increased bioavailability and decreased toxicity(FA. Olotu et al., 2018). In our previous in silico study, Geraniin was identified as a potential anti-Ebola candidate. A pharmacophore model generated from Geraniin, showed that there were three aromatic rings, a hydrophobic ring and several hydrogen donors/acceptors responsible for anti-Ebola activities (Boadu et al., 2021). This model could be a volatile or contaminant of Geraniin. Hence, Geraniin was subjected to GC-MS analysis to identify possible volatile(s) that could be close to the pharmacophore model and to also create uniformity in methodology used in the identification of antiviral phytochemicals in the alcoholic leaf extracts and also to identify the active volatile compound(s) (Chauhan et al., 2014). Twenty (20) fragments of compounds were identified from the chromatogram of Geraniin as indicated in Table S9. Out of the 20 compounds, 1,2-Benzenedicarboxylic acid, butyl 2-methyl propyl ester was the only compound that has been reported in the literature to possess anti-viral and antimicrobial activities (FUNGI, Govindappa et al., 2014). Hence its use in molecular docking in this present study.
Table 2, summarises selected phytochemical compounds from GC-MS analysis of crude and fractionated extracts and Geraniin (98 %w/w) with reported anti-viral properties. It also shows the computed physicochemical descriptors as well as predict Absorption, Distribution, Metabolism, and Excretion (ADME), of the identified anti-viral phytochemicals.
The physicochemical and pharmacokinetic properties in the early days of the inception of drug discovery were normally predicted and the last stage of the drug design process, but it is important to predict ADME properties of the potential drug candidate, to decrease the cost of drug discovery research as ADME, normally contributes to failures of drug molecules of more than 50% (Mandlik et al., 2016).
This study identified a monoterpene, p-Cymene, in the SMM crude and SMEH fractions of S. mombin leaf extracts. p-Cymene in literature has been reported to possess anti-viral, anti-oxidant, anti-inflammatory, anti-parasitic, anti-diabetic, anti-fungal, and anti-cancer effects in both in vivo and in vitro studies of the molecule (Panikar et al., 2021, Balahbib et al., 2021, Sharifi-Rad et al., 2018) In addition, a derivative of p-Cymene known as Thymol with a percentage composition of 0.5% and 0.21% was found in SMM and SMEDCM respectively with reported antimicrobial, anti-inflammatory, anti-oxidant activity (Braga et al., 2006) and anti-viral properties against spike glycoprotein of SARS-CoV-2 (Kulkarni et al., 2020). Furthermore, D-Limonene, another monoterpene, was detected in SMMDCM with a percentage composition of 0.34 %, has been reported to possess anti-SARS-CoV-2 activity in silico(Panikar et al., 2021) and antimicrobial properties in vitro (Zahi et al., 2015).
Reported by other authors, L-alpha-Terpineol, a monoterpenoid, is known to exhibit various pharmacological activities such as anti-Covid-19 activity in silico (Gul et al., 2020), anticonvulsant, sedative, antinociceptive, and hypotensive effects (Aronsson et al., 2017, Khaleel et al., 2018). We identified L-alpha-Terpineol in both SMMH and SMEH with percentage composition of 0.44% and 1.40%, respectively. The phytochemical L-alpha-Terpineol has been reported to have anti-CoVID-19 properties in silico by (Panikar et al., 2021), while its anti-oxidant and disinfectant properties were identified by (Cours, 2020).
In terms of Geraniin (98% w/w), we have reported in our previousin silico study to possess anti-Ebola and anti-SARS-CoV-2 properties against EBOV secreted Glycoprotein (sGP) and a possible inhibitor interferes with the functioning of SARS-CoV-2 targets (Boadu et al., 2022, Boadu et al., 2021). During the anti-Ebola study, a pharmacophore model generated showed that three aromatic rings, a hydrophobic ring and several hydrogen donors/acceptors were responsible for ant-Ebola activities, although it violated Lipinski’s rule of five (Lipinski, Lipinski et al., 1997).
Table 2 : Summary of identified anti-viral phytochemical compounds from GC-MS analysis of SM crude and fractionated leaf extracts with their reported pharmacological action and computed physicochemical descriptors as well as predict Absorption, Distribution, Metabolism, and Excretion (ADME), of the identified anti-viral phytochemicals.