Figure 2 depicted the tree and the leaves of the A. scholaris. The bark is of the tree is dark-brown in color with smooth texture and milky latex 20.The leaves are non-stipules, with about 5–8 whorls. The petiole has a width of about 2 cm diameter and stout and flowers are ephemeral, with axillary cymes arrangement made of greenish-white color 21. The leaf is made up of medium to large size dorsiventral blade The venation of the leaf is pinnate, consisting of large number of veins 30.
The result of phytochemical analysis of the A. scholaris leave extracts in the various solvents are presented in Table 1. It has shown flavonoids and alkaloids presence at higher proportions, in both solvents in comparison to other phytochemicals. The methanol extract has shown the presence of all metabolites, with exception of proteins, anthraquinone and reducing sugar. The aqueous extract contained reducing sugar, amino acid, phenolic compounds, anthraquinone and saponins. Of all, ethyl acetate and chloroform contained the lowest amount of the bioactive molecules. According to Anthony et al., the extracts of the leave contained the most essential compounds in the ethyl acetate, butanol and water as the extracting solvents 27. Additionally, higher proportions are present in the bark and leaves of the aqueous. The most detected ones where; proteins, steroids, phenols and tannins 27. In a qualitative comparative review presented by Khyade et al., for the phytochemical screening of A. scholaris leaves, most of the studies conducted have majorly reported carbohydrates, oils and fats alkaloids, flavonoids, tannins, terpenoids, saponins and steroids. For instance, Misra et al., reported that extract of n-hexane has alkaloids and steroids as metabolites. However, the isopropanol extract of the leave has shown the terpenoids in smaller quantity in comparison to root Mistry and bark of the plant. Mistry and Parekh was observed oils and fats, alkaloids, flavonoids, terpenoids, glycosides, saponins, mucilage and gums in both bark, leaves and stem of the plant 31.
Table 1
Screening of phytochemical in the extracts of A. scholaris
Analytical parameters | n-hexane | Chloroform | Ethyl acetate | Methanol | Water |
Steroids | - | - | + | + | - |
Alkaloids | + | + | - | - | - |
Dragendoff test | + | + | + | + | + |
Mayer’s test | - | - | - | - | - |
Flavonoids | + | + | + | + | + |
Protein | - | - | - | - | - |
Amino acid | - | - | - | + | + |
Reducing sugar | - | - | - | - | + |
Tannins | - | - | - | + | + |
Anthraquinone | + | + | + | - | + |
Saponins | - | - | + | + | + |
Glycosides | + | + | - | + | - |
Key: (+) indicates presence, while (-) indicates absence |
Thus, we analyzed the antimicrobial properties of the A. scholaris plant. The results from the assessment of the antibacterial properties E. coli and S. aureus has been determined. It has shown the effects of extracts on the chosen bacterial pathogens under the zone of inhibitory study.
Table 2–5 have shown the antibacterial activities on the crude extracts. The results revealed the excellent inhibition against the growth of all the bacteria tested at predetermined studied concentrations. For n-hexane (Table 2), chloroform (Table 3), ethyl acetate (Table 4) and methanol (Table 5) extracts, S. aureus has the highest activity while E. coli has the lowest. Methanol extract also demonstrated the highest inhibitory effect for the studied organisms. Previous finding from Thankamani et al., revealed the effect of extract of methanol which possessed the highest inhibition against the microorganism and was more pronounced at the inhibitory zone of 15–25 mm. Whereas chloroform extract has less inhibition effect for the S. aureus 32. Accordingly, the inhibitory effect of n-hexane and ethyl acetate extract was closely the same with only slight variation for the studied organisms. Study conducted by Anthony et al., reported that methanol extracts of A. scholaris leaf exhibited much significant antibacterial activities in comparison to other extracts employed 33.
Table 2
Antibacterial effect of extract of n-hexane for A. scholaris leave against the tested bacteria
Microorganisms | Concentration (mg/mL) |
| 40 | 20 | 10 | 5 | 2.5 | 1.25 |
Zone of inhibition (mm) |
E. coli | 6 | 4 | 3 | 2 | 2 | 2 |
S. aureus | 7 | 6 | 6 | 4 | 3 | 3 |
Table 3
Antibacterial activities of extract of chloroform for A. scholaris leave against the tested bacteria
Microorganisms | Concentration (mg/mL) |
| 40 | 20 | 10 | 5 | 2.5 | 1.25 |
Zone of inhibition (mm) |
E. coli | 15 | 12.5 | 10 | 8 | 5 | 3 |
S. aureus | 13 | 13 | 12 | 10 | 8 | 5 |
Table 4
Antibacterial effect of extract of ethyl acetate for A. scholaris leave against the tested bacteria
Microorganisms | Concentration (mg/mL) |
| 40 | 20 | 10 | 5 | 2.5 | 1.25 |
Zone of inhibition (mm) |
E. coli | 10 | 9 | 7 | 5 | 3 | 1 |
S. aureus | 9 | 8 | 6 | 4 | 3 | 2 |
Table 5
Antibacterial effect of extract of methanol for A. scholaris leave against the tested bacteria
Microorganisms | Concentration (mg/mL) |
| 40 | 20 | 10 | 5 | 2.5 | 1.25 |
Zone of inhibition (mm) |
E. coli | 23 | 21 | 20 | 17 | 13 | 9 |
S. aureus | 21.5 | 20 | 19.5 | 18 | 15 | 11 |
Biological route for the nanoparticle’s synthesis using plant materials has a lot of advantages over synthesis techniques. It is ideal for a large-scale synthesis of the nanoparticles. The biosynthetic route is suitable and economical for the Cu-NPs synthesis for environmental, medical, as well as industrial applications. In addition, it eliminates the use of toxic chemical substances which are potentially hazardous to the living organisms and the surrounding environments. Thus, an aqueous extract of the A. scholaris leave was employed for the Cu-NPs biosynthesis. The Cu-NPs was confirmly synthesized by the color changes reacting species according to the UV-visible spectroscopy 34. Addition of the leaf broth to the CuSO4.5H2O solution, resulted in the color changes from light to dark green, confirming the successful formation of the Cu-NPs (Fig. 3). In a previously study, the formation of the dark green color which eventually changed to dark brown, reaffirmed the successful biosynthesis of the Cu-NPs. Also, the color change was attributed to the excitation resulting from surface Plasmon resonance (SPR) 35. The spectrum was determined at 200–800 nm wavelength range (Fig. 3). The spectrum from UV-vis has 243 nm as the stable wavelength for the formation of Cu-NPs 36.
The FTIR spectrum revealed the various functionalities in the Cu-NPs. It revealed various interactions as well as compositions of the leave extract (Fig. 4). The presence of broad peak at 3137.35 cm− 1 highlighted the stretching due O–H from the alcohols and carboxylic acid present in the compounds 376. The intense peak appeared around 1733.46 cm− 1 represents C = O bending vibrations. Also, appearance of the IR peak at 1639.03 cm− 1 shows the stretching occurred for C = C in the compounds. The peak at 1372.06 cm− 1 was due to S = O vibration, while the peak at 1071.52 cm− 1 indicated the stretching due to C–O band of the primary alcohols. Peak at 870.44 cm− 1 shows C–H bending in the molecules, while the peak at 599.21 cm− 1 was a result of C–I vibration of the halo species. The occurring of peak around 449 cm− 1 corresponding on the of Cu ion specie. The FT-IR spectrum confirmed the possibility of the various interactions between the copper ion and the various functional groups contained in the extract 30. Thiruvengadam et al., stated that the interaction between the Cu-NPs and the metabolites in the A. scholaris resulted in the possible reduction the NPs to copper as confirmed by the FTIR result 36.
The images from SEM result depicted the synthesized CuNPs, with the surface particles having irregular shapes consisting of triangular, cylindrical, polygonal, and nearly spherical as shown in Fig. 5. Similar outcomes were reported, in which, SEM images of the synthesized Cu-NPs contained irregular particles arranged in clusters comprising of different structures from polygons to spherical shapes 36. The EDX spectrum explained the elements composition on the surface of the Cu-NPs. The mapping result highlighted the major elements present (Fig. 6). The carbon and oxygen are appeared as the lowest peaks compared to the Cu. They resulted from the phytochemical metabolites present in leave extract 12. Thus, they also served as the evidence for the for the reduction of Cu-NPs to Cu ions. The compositions of the elements from the EDX spectrum were depicted in Fig. 7. The Cu peak indicated that Cu-NPs has the purest form of copper ion with the relative abundance of 67.41%, followed by the O and C with the relative abundance of 21.17 and 11.42%, respectively. This is contrary to the previous findings with much lower abundance of the Cu with the Cu content of 26.06% and 8.04%, respectively 3438. Thus, this result findings indicated that A. scholaris could be well utilized for the biosynthesis of Cu-NPs.