The sugarcane bagasse (SB) used in this experiment was provided by Quena Company for Paper Industry in Quena, Egypt, and the paraffin oil was obtained from Sigma-Aldrich in St. Louis, MO, USA. Neither the SB nor the paraffin oil underwent any further purification before being used in the experiment.

The aerial parts of C. frutescens were collected from the National Research Centre gardens in spring, according to the national institutional guidelines and regulations. The plant was authenticated at the Agricultural Museum, Dokki, Giza, Egypt, and a voucher sample was kept at the herbarium of the National Research Center (No. M218). The fresh plant (flower heads and leaves) was placed in a conical flask with distilled water, and the volatile oil was obtained by the hydro-distillation method using a Clevenger apparatus. The oil was stored in a clear glass vial for GC/MS analysis [15].

SB (150 g) underwent a multi-step process. Initially, it was hydrolyzed using dilute hydrochloric acid (1.5%) at 120°C for 2 h. Subsequently, the resulting material was converted into pulp by treating it with sodium hydroxide (20 g in 300 mL water) at 170°C for 2 h. The obtained pulp (80 g) was then subjected to a bleaching process involving chlorite (3%) and acetic acid (1.7 mL) at 80°C for 2 h to eliminate lignin, resulting in pure α-cellulose. Throughout the bleaching stage, acetic acid was continuously added to maintain a pH between 1 and 3, ensuring optimal reaction conditions [9,16].

Pure α-cellulose (2.5 g) was dissolved in isopropanol (75 mL) and reacted with sodium hydroxide (40%, 3 g in 7.5 mL water) and monochloroacetic acid (3 g) for 3.5 h at 55°C with constant stirring. The resulting carboxymethyl cellulose (CMC) was precipitated by adding 70% ethanol, filtered, and dried [13,16].

The process involved treating CMC (1.6 g; DS = 0.7) with DMSO (35 mL) and stirring until complete dissolution. The stearic acid (3 g) was mixed with acetic anhydride (2 mL) and a few drops of sulfuric acid as a catalyst. This mixture was stirred at 90°C until it became viscous for 30 min, then filtered, washed with ethanol, and finally dried.

The performance of amphiphilic CMC–Stearate as a dispersant was investigated by mixing CMC–Stearate (0.5 g) with water (1.5 mL). The oil (with different weight percentages of 2.5%, 5%, and 10%; denoted as CMCS1, CMCS2, and CMCS3, respectively) was added by mixing through an Ultrasonicator (700 W; Sigma-Aldrich) for 3 min in an ice water bath [17].

The qualitative tests were performed by the disc diffusion method using nutrient agar plates [20]. Inoculations of pathogenic microorganisms used in this study included the gram-positive bacteria Bacillus cereus, Micrococcus luteus, and Staphylococcus aureus; the gram-negative bacteria Escherichia coli and Helicobacter pylori; and the pathogenic yeast Candida albicans.

The analysis used Excel software for particle size distribution. To ensure accuracy, each experiment was repeated three times, and the reported results represent the average of three samples with less than 5% variation.

The yield of the volatile oil extracted from the aerial parts of C. frutescens using the hydro-distillation method was 0.11% v/w. Based on their mass spectrum data (MS), 36 metabolites were identified using the Wiley spectral library collection, GNPS, and NIST library database [20]. The total percentage of identified compounds was estimated to be 68.7%. The distribution of the main essential oil classes of C. frutescens investigated is shown in (Fig. 1).

Volatile oil constituents along with their respective retention times (Rt), experimental Kovats retention index reported in the investigation (KI*), Kovats retention index from the literature (KI**), and percentages are listed in (Table 1, Fig. 1).

As illustrated in Fig. 2, oxygenated monoterpenes (28.54%) and sesquiterpene hydrocarbons (27.23%) were the predominant classes, while alkanes, monoterpene hydrocarbons, and oxygenated sesquiterpenes were demonstrated at moderate levels (4.8%, 3.11%, and 2.49%, respectively). Contrariwise, benzenoids were present with a percentage of 0.71, and the percentage of oxygenated diterpenes was 1.82 under hydro-distillation conditions.

Oxygenated monoterpenes were the predominant class in C. frutescens essential oil extracted (28.54%). The most privileged-identified compounds are dihydrocarveol and isopulegol acetate, which occurred with relative percentages of 12% and 5.5%, respectively. Dihydrocarveol is used as an important additive in the flavor industry and as a building block in the synthesis of natural products [21].

Also, the most abundant sesquiterpene hydrocarbons were β-caryophyllene (15.7%), followed by aromadendrene (6.85%). β-caryophyllene has antioxidant, anticancer, cardioprotective, hepatoprotective, nephroprotective, immunomodulatory, gastroprotective, and antimicrobial activities [8,22]. While aromadendrene is used to produce environmentally friendly insecticides against cereal pests, it also has anticholinesterase, antinociceptive, anti-hyperalgesic, and anti-mycobacterial activities [22]. 2-methyl decane was an abundant alkane present in the oil (4%). 1, 3, 8-p-menthatriene was the major monoterpene hydrocarbon (2.4%). Nerolidol (1.71%) was presented as a major oxygenated sesquiterpene. It possesses pharmacological and biological activities such as anti-biofilm, anti-microbial, anti-parasitic, antioxidant, anti-inflammatory, anti-ulcer, skin penetration enhancer, insect repellent, and anti-cancer effects. Nonetheless, verticiol (1.82%) was the only oxygenated diterpene detected; similarly, benzenoids were present at far lower quantities (0.17%). Notice that the antimicrobial activities of the essential oils of various Chrysanthemum species against a wide range of microbes were investigated, aiming to use these plants and their oils as natural spices and preservatives in food and pharmaceutical preparations, along with other various applications [3,23].

TEM analysis revealed that CMC-Stearate formed irregular honeycomb structures with a radius of 0.12 μm (Fig. 5). However, upon nanoemulsification, CMCS1 transformed into discrete, rounded particles ranging from 2.46 to 3.51 nm in diameter, demonstrating its effective dispersion capabilities.

TEM analysis revealed a striking morphological transformation from the irregular honeycomb structures of CMC-Stearate to discrete, spherical nanoparticles in CMCS/2.5% oil (i.e., CMCS1). This transition is crucial for the formation of stable nanoemulsions. The spherical nanoparticles, with their high surface area and reduced particle size, effectively adsorb at the oil-water interface, acting as Pickering stabilizers. The compact and spherical morphology minimizes interfacial energy, enhancing the stability of the nanoemulsion against coalescence and Ostwald ripening. Additionally, the smaller particle size contributes to improved colloidal stability and prevents sedimentation. This morphological change, induced by the esterification of CMC with stearic acid, underscores the importance of molecular design in tailoring the properties of nanomaterials for nanoemulsification applications.

The standard well diffusion assay was used to record the inhibition zone [16]. Table 2 and Fig. 6 show that the CMCS1, CMCS2, and CMCS3 had strong antimicrobial activity against Escherichia coli, with inhibition zones of 17, 18, and 21 mm, while only CMCS2 and CMCS3 had strong antimicrobial activity against Staphylococcus aureus, with inhibition zones of 20 and 22 mm. The CMCS1 didn’t give any inhibition zone against Staphylococcus aureus. This activity is likely due to a combination of volatile and non-volatile compounds in the material [26]. The CMCS3 exhibited a stronger antibacterial activity against Escherichia coli and Staphylococcus aureus than CMCS1 and CMCS2 due to their low content of C. fructescens.

The standard well diffusion assay used in this study gave a higher inhibition diameter compared to the disc diffusion method.

The activity profile for MICs of C. fructescens extracts (Table 3) appeared to give super antibacterial activity against all types of bacteria. In addition, CMCS3 gave the best antibacterial activity (i.e., 100.00%, 85.20%, 80.00%, 100.00%, and 76.43% against Escherichia coli, Helicobacter pylori, Bacillus cereus, Staphylococcus aureus, and Candida albicans) due to its high content of C. fructescens.