Formulation and Evaluation of Green Synthesis of Copper Nanoparticles from Neem and Coconut

Copper nanoparticles (CuNPs) and copper oxide nanoparticles (CuONPs) are nanoscale particles whose diameter is generally 1 nm -100 nm [1]. They have a large surface-to-volume ratio which gives them specific physicochemical properties, such as a great catalytic power, optical properties and antimicrobial activity. This antimicrobial effect occurs as a result of the regulated discharge of Cu2 + ions, which cause damage to bacterial cell membranes, produce reactive oxygen species (ROS) and disrupt essential cellular enzymes [2], [3].

Safety, cost-effectiveness, and oral antimicrobial agents with a broad spectrum are urgently needed in pharmaceutical industries to fight the multidrug-resistant pathogens as a support of the wound healing process and topical drug delivery. CuNPs satisfy these requirements due to their low toxicity to mammalian cells and excellent inhibitory effects against some of the prevalent pathogens like Escherichia coli, Staphylococcus aureus and Pseudomonas aeruginosa [4], [5].

Conventional physical and chemical methods of synthesis use certain toxic reducing agents (e.g. sodium borohydride, hydrazine), organic solvents, high temperatures, and large amounts of energy. These systems produce harmful wastes and raise the costs of production and are not very appropriate to use in pharmaceutical purposes [1], [6].

Green synthesis overcomes these shortcomings by using plant extracts as natural reducing, capping as well as stabilizing agents. Phytochemicals that include polyphenols, flavonoids, terpenoids and polysaccharides can result in reduction of metal ions under light aqueous conditions to biocompatible and environmental friendly nanoparticles [7].

The extracts of the Neem (Azadirachta indica) leaf are especially efficient because of the presence of azadirachtin, nimbin, quercetin, and other polyphenols that degrade Cu 2+ to which Cu 0 or Cu O are very quickly reduced [8], [9]. Extracts of copra (Cocos nucifera), water, and even the husk provide lauric acid and sucrose and proteins which increase colloidal stability and inhibit aggregation [10], [11].

Both plants are inexpensive, widely grown and can be locally found in the tropical areas like India which makes scaling and making the plants use cost-effective in pharmaceutical use [12].

The current review relies specifically on peer reviewed articles published in 2021-25. It gives detailed overview of the green formulation, characterization, evaluation and pharmaceutical use of CuNPs/CuONPs based on neem and coconut extracts with focus to antimicrobial and wound-healing properties, safety assessment, and stability of the formulations.

The key messages are the introduction of the topic in simple and clear terms the B.Pharm and M.Pharm students may understand and the desire to conduct practice experiments that apply the knowledge with the help of simple materials and basic laboratory equipment.

The paper has been structured as follows; fundamentals of copper nanoparticles, plant extracts involved, the methodologies of formulation, methods of characterization, analyses of the nanoparticles, pharmaceutical applications, issues and solutions, prospects and conclusion.

2. Basics of Copper Nanoparticles

2.1 Properties and Pharmaceutical Uses

Metal nanoparticles are copper nanoparticles also known as copper nanoparticles (CuNPs) and copper oxide nanoparticles (CuONPs) with sizes ranging between 1-100 nm [1]. They have a large surface to volume ratio. This ratio provides them with special optical, catalytic and biological characteristics.

CuNPs release Cu²⁺ ions slowly. These ions destroy cell membranes of bacteria. And they also produce reactive oxygen species (ROS). ROS destroy proteins and DNA within microbes [2], [3].

CuNPs are useful antimicrobial agents in the field of pharmacy. Zones of inhibition of 18-25 mm were obtained on Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa with green CuNPs synthesized using as the extract of neem leaves. The minimum concentration of inhibition was 25 to 75 µg/mL [4], [5].

The effect of CuNPs on wound healing is also supported. They enhance fiberblast growth and collagen production. They reduce inflammation. A recent study found that rat models had 80-85 percent wound closure in 12-14 days [6].

Drug-delivery carrier and antioxidant agent are also other applications.

2.2 Why Green Synthesis is Better

The reduction with the help of toxic reductants, including sodium borohydride or hydrazine, is used in traditional methods of chemical synthesis. These techniques have great energy-consumption requirements and lead to production of hazardous wastes [7].

Plant extracts in the green synthesis are employed as reducing and capping agents. Phytochemicals: These drugs apply mild conditions (NO₂, aqueous solution) [1], [8].

Green CuNPs are less toxic on human cells. Their toxicities to normal fibroblasts regularly make an IC₅₀ excess of 100 µg/mL, and chemically engineered CuNPs have toxicity less than 50 µg/mL [9].

Green processes are also inexpensive, biodegradable and friendly to the environment.

Table 1: Antimicrobial activity and particle characteristics of green CuNPs

Figure 1: Schematic showing mechanism of antimicrobial action of green CuNPs (Cu²? release and ROS generation

3. Plant Extracts Used in This Review

Neem and coconut are also very cheap and plentiful plants in tropical nations such as India. Their extracts also have phytochemicals which reduce copper ions and stabilize the nanoparticles that occur. These extracts have been employed recently (2021-2025) in the synthesis of green CuNP_s and CuONP_s either individually or in combination.

3.1 Neem (Azadirachta indica) Leaf Extract

Neem leaves contain high concentration of polyphenols, flavonoids (quercetin) as well as terpenoids and tannins. Those compounds will donate electrons to decrease Cu^{2 +} to Cu⁰ or CuO and capped the nanoparticles to avoid aggregation [12], [13].

 Gurudevi and Sirisha (2024) used fresh neem leaves boiled in 15-20 whose aqueous 10% (w/v) extract was prepared using boiling and then served its availability. The dropwise addition was 0.1 M CuSO₄ solution stirred with the filtered extract at 60 ^oC. Nanoparticle formation was proved when the colour turned blue to dark brown. Analysis revealed a 18-40 nm sphere in the shape of a particle. The nanoparticles exhibited powerful antimicrobial properties having zones of inhibitions of 20-24 mm to S. aureus [14].

Muley et al. (2023) used a similar procedure of boiling. Their CuNPs were 22-35 nm in size (TEM), -28 mV (characterized by good stability) and 25-75 ug/mL (against common pathogens). The authors have observed how easy the process is and it can be applied in undergraduate laboratories [15].

Neem seed extract was utilized to carry out green combustion by Kalaivani et al. (2024). They combined the extract with copper sulphate and set it fire. CuO nanoparticles obtained were 15-50 nm, crystalline (monoclinic phase), and exhibited other photocatalytic and anticancer property on top of anti-microbial properties [16].

 It has been used in a neem-leaf-novel form of CuO nanoparticle through a study on 2025 to preserve the mango after harvest. The particles minimized the fungal spoilage and preserved the quality of the fruit with extremely low cytotoxicity [17].

3.2 Coconut (Cocos nucifera) Copra/Water Extract

In coconut copra, husk, and water, there are lauric acid (≈50 % of fatty acids), sucrose, proteins, and polysaccharides. Lauric acid is broken down to monolaurin which not only destroys microbial membrane but is a capping agent to enhance dispersion [18].

In the preparation, Madhusha et al. (2023) used coconut coir aggravated into activated carbon and impregnated with copper. The CuNPs contained in it measured 30-48 nm and exhibited good suspension through aqueous solutions, which provided improved stability to antimicrobial composites [19].

Asiri et al. (2025) characterised the preparation of bimetallic Ag-Cu nanoparticles by using aqueous coconut husk extract. Silver and copper ions reduction by the husk phytochemicals was performed concomitantly, to form a spherical particle of 42.5 ± 1.5 nm (TEM). The coconut extract enhanced colloidal stability and reduced general toxicity in relation to those that have been synthesised chemically [20].

CuNPs with pure coconuts extract alone in less research have been performed, though the components have been shown to increase the stability of the particles in most cases when utilized with additional plant extracts.

Figure 2: Key phytochemicals in neem (quercetin, azadirachtin) and coconut (lauric acid) responsible for CuNP synthesis

4. Formulation Methods for Synthesis

The green synthesis of the copper nanoparticles is based on the simple and low cost processes with the use of plant extracts in aqueous. According to the recent studies (2021-2025), the reliable protocols are defined with the neem leaf extract and coconut-derived extracts. Their application can be done in simple glassware, by a hot plate, and a centrifuge in a college pharmacy laboratory.

4.1 Step-by-Step Green Synthesis Process (combine neem + coconut extract)

The extracts are made separately and then combined to enhance greater stability and yield.

Neem leaf extract - Fresh whole neem leaves should be taken. Wet them with a lot of running tap water and distilled water. Cut 10g of leaves in small pieces. Boil in 100 mL distilled water with 10- 15 min at 80-90 ^oC. Filtered; cool, pass through Whatman No. 1 paper in clear filtrate [21], [22].

Coconut extract - Use fresh husk of coconut or copra. Grate or grind 20g of husk/copra into a fine powder. Using 100 mL of distilled water, soak or boil up to 30-60 min (or alternatively soak at room temperature up to 48 h and then heat at 100 ^o C up to 60 min, as in Asiri et al., 2025). Filter the extract [23].

Combined synthesis - Blend an equal amount (e.g. 50 mL each) of neem and coconut extracts. Magnetic stir the mixture until heated (60-80 ^o C). Stir in 100 mL of 0.01-0.1 M CuSO?·5H?O solution drop by drop, and stir 30120 min until colour changes to dark brown/greenish-brown (formation of CuNPs/CuONPs).

Centrifuge the suspension with 8000-10 000 rpm for 15 min. Wash the pellet three or four times with distilled water and ethanol. Dry at 60-80 ^oC or in a vacuum oven. Grind to fine powder, where necessary [21], [23], [24].

Yield is typically 70-90 %. It lasts 2- 3 h and does not need any special equipment.

4.2 Role of Phytochemicals

Neem extracts have polyphenols (quercetin, nimbin), flavonoids and terpenoids. These release electrons and reduce Cu ²⁺ ions to Cu⁰ or CuO. They also capped the nanoparticles and they stop aggregation [21], [22].

Coconut extract is a rich source of lauric acid, sucrose, proteins and polysaccharides. Lauric acid and monolaurin enhance dispersion and long term colloidal stability. Additional capping agents are proteins [23], [24].

The FTIR spectra used in published reports indicate peaks at 3400 cm?¹ (O–H stretch), 1620-1630 cm ^-1 (C=O), and 1050 cm ^-1 (C -O), which indicate the presence of plant molecules on the surface of the nanoparticle.

Figure 3: Flowchart of combined neem + coconut green synthesis of CuNPs/CuONPs

5 Characterization Techniques

Different indistinct methods are employed by the researchers to ascertain the formation, size, shape, purity, and stability of the green-synthesized copper nanoparticles. These are easy, readily accessible, in college laboratories, and provide credible results. However, the recent research (2021-2025) regarding neem- and coconut-derived CuNPs/CuONPs provides stable data results.

5.1 Physical Methods (UV-Vis, TEM, SEM)

The fastest method of confirming the formation of nanoparticles is by use of UV-Vis spectroscopy. A blue colour shift is visible to brown-green, and an absorption peak (surface plasmon resonance) develops between 340-620 nm, depending either on the formation of Cu0 or CuO. The fastest method of confirming the formation of nanoparticles is by use of UV-Vis spectroscopy. A blue colour shift is visible to brown-green, and an absorption peak (surface plasmon resonance) develops between 340-620 nm, depending either on the formation of Cu⁰ or CuO.

The peak of CuO nanoparticle prepared by using ethanolic neem extract was found to be high at 344nm, assured by Khairy et al. (2024). Patel et al. (2025) showed a wide peak at 550-600 nm for neem mediated CuO nanoparticles.

TShape and size can be seen by the use of transmission electron microscopy (TEM) and scanning electron microscopy (SEM). Their particles are predominantly rounded or semi rounded.

• Khairy et al. (2024): semispherical, 10.7–30.9 nm
• Patel et al. (2025): spherical, mean size 50.93 nm (HR-TEM)
• Madhusha et al. (2023): coconut-coir-derived CuNPs, 30–48 nm

SEM exhibits the homogenous distribution and surface morphology. EDX identifies high copper of plant capping with the small percentages of C and O

5.2 Chemical Methods (XRD, FTIR)

X-ray diffraction (XRD) ensures the determination of crystalline structure. CuO derived by neem normally exhibits monoclnatine phase; CuNPs exhibits face centred cubic copper.

Patel et. al cited 2025 found clear monoclinic CuO peaks. Crystalline CuO was also obtained by Kalaiyan et al. (2025).

The Fourier-transform infrared spectroscopy (FTIR) determines plant molecules on the nanoparticle surface.

Typical peaks:

• 3400–3200 cm?¹ (O–H stretch from polyphenols)
• 1620–1630 cm?¹ (C=O)
• 600–400 cm?¹ (Cu–O bond)

Khairy et al. (2024) have demonstrated good Cu-O bands of 611 cm?¹ and 463 cm?¹ and plant carbonyl peaks of 1627- 1669 cm?¹.

Several measures determined colloidal stability are dynamic light scattering (DLS) and zeta potential measurement. Zeta between -25 and -35 mV implies that there is good repulsion and long-term stability.

Patel et al. (2025) Zeta potential was noted at-32.50 mV.

Figure 4: Typical UV-Vis spectrum of neem–coconut CuNPs

6. Evaluation of the Nanoparticles

The size, shape, stability, antimicrobial activity, and safety of green-synthesized copper nanoparticles need to be assessed in order to use as a pharmaceutical. In the recent studies (2021-2025), such standard protocols as TEM, DLS, disk diffusion, MIC determination, MTT assay, and hemolysis test are involved. These tests indicate that CuNPs/CuONPs synthesized by the use of neem and coconuts can be of pharmaceutical interest.

6.1 Size, Stability, and Shape Control

TE M and SEM exhibit semispherical or spherical particles. Sizes range from 10-60 nm.

The size of semispherical CuO nanoparticles (neem extract) reported by Khairy et al. (2024) is 10.7-30.9 nm.

 Muley et al. received 22-35nm-spherical particles of the neem leaf extract (2023). The data of -25 and -35 mV on zeta potential illustrates very high colloidal stability. In aqueous media, the particles do not agglutinate.

DLS provides hydrodynamic diameter 30-70 nm which is somewhat larger than dry size because of the capping layer on the plant.

The level of shape is based on extract concentration and temperature. Recent higher ratio and 60-80 ^oC reaction temperature result in lowest, homogeneous particles.

6.2 Antimicrobial Activity and Safety Tests

The most common tests are disk diffusion and broth micro diffusion.

The article by Khairy et al. (2024) compared neem-derived CuO NPs to multidrug-resistant clinical isolates. Areas of inhibition were 19-34mm (Gram-negative) and 28-32 mm (Gram-positive). MIC values were 62.5–125 µg/mL. MBC/MIC ratio = 1 indicated that the nanoparticles were bactericidal.

According to Gurudevi and Sirisha (2024), the zones were 20-24 mm in the case of S. aureus and 30–50 µg/mL MIC.

It was found that 18 mm was against E. coli and 15 mm was against S. aureus (Muley et al. 2023).

Safety is equally important. Khairy et al. (2024) obtained 383–403 µg/mL on human skin fibroblasts (HBF4 cell line) - significantly higher than therapeutic levels of antimicrobials.

Hemolysis was <5 % at 100 ug/mL. The antioxidant (31-92%), antibiofilm (62-95%) activity is an added advantage in the wound-healing formulations.

Stability is advanced by extracts attained through coconut, or mix of coconuts, without toxicity.

Table 2: Antimicrobial and safety data of green CuNPs/ CuONPs

Figure 5: Representative agar plates showing zones of inhibition of neem–coconut CuNPs against E. coli and S. aureus

7. Pharmaceutical Applications

Copper nanoparticles generated by green synthesis using neem and coconut extracts (i.e. CuNPs/CuONPs) have a high potential in pharmaceutical applications. They play an anti-microbial role, wound-healing, and drug carrier roles. Recent investigations of 2021-2025 emphasize that they are low-toxic, well-stable, and they concur with phytochemicals of plants.

7.1 Antimicrobial Agents and Wound Healing

The multidrug-resistant bacteria are killed by neem-derived CuO nanoparticles. In Khairy et al., ethanolic neem extract was used to prepare CuO NPs (10.7-30.9 nm). These NPs provided 19-34mm zone of inhibition with Gram-negative pathogens and 28-32 mm with Gram-positive. MIC values were 62.5-125 µg/mL. The antibiofilm level (62-95 %) and low level of cytotoxicity (IC?? 383–403 µg/mL  on skin fibroblasts) were also demonstrated by the NPs [28].

The system used to synthesize neem CuNPs was aqueous (20-60 nm). These particles had both bigger areas of inhibition in comparison to those produced by neem extract (18 mm vs E. coli, 15 mm vs S. aureus). The authors provided a conclusion that CuNPs in combination with neem phytochemicals have a high potential of wound healing formulations [29].

General The general effect of green CuNPs on wound healing is a variety of processes. The plant extract was used to prepare CuNPs (10-85 nm) by Saeedi et al. (2025). The particles elevated fibroblast growth (maximum 29.78%), hastened the healing of scratch-wounds, facilitated angiogenic expression genes (VEGF-A, HLA-G5), as well as diminished pro-inflammatory cytokines. CC?? was 291.6 µg/mL which ensured safety of topical use [30].

Patel et al. (2025) using neem CuO NPs for post-harvest fungal infections control in mango. The particles were of low mammalian cytotoxicity with preservation of the fruit quality, which suggested that they can be applied topically safely.

These results indicate that neem-c coconut CuNPs could be formulated into creams or dressings to reduce infection and reduce the time to healing.

7.2 Drug Delivery and Other Uses

CuNPs are used as a carrier of antibiotics/anti-inflammatory drugs. Muley et al. (2025) mentioned high surface area and plant capping, which permits an effective loading and release of drugs [29].

Coconut extracts enhance the colloidal stability of the NPs and thus the NPs can be included in the hydrogel or cream formulations. Asiri et al. (2025) employed coconut husk to prepare stable Ag-Cu NPs that are low toxicity and high cellular uptake and which could find application as a model of targeted delivery.

Some other applications are on nano-pesticides, catalysts and food packaging. These NPs are sustainable due to their green properties and low prices.

Table 3: Pharmaceutical applications of green CuNPs/CuONPs

Figure 6: Schematic of green CuNP-loaded hydrogel for wound dressing