Salinity stress is a major environmental threat in agricultural systems. Kenaf is a promising crop for the future for cultivation in salinity-affected soils because of its high phytoremediation potential. The current study aimed to investigate the effects of salt stress using six different sodium chloride (NaCl) concentrations (0, 50, 100, 150, 200, and 250 mM) on the plant growth, physiological characteristics, bioactive constituents, and antioxidant capacity of H. cannabinus. The results indicated that the NaCl stress induced significant reductions in plant height and in the dry and fresh weights of the leaf tissue. In addition, the K, Ca, Mg, and P concentrations in this tissue also decreased under NaCl stress treatment conditions. In contrast, the NaCl stress led to the accumulation of hydrogen peroxide (H₂O₂), superoxide anion (O₂^•−), malondialdehyde (MDA), proline, total soluble sugar, and total soluble protein. Under NaCl stress, the levels of antioxidants, including phenolics and flavonoids, also increased. The gas chromatography–mass spectrometry (GC-MS) results showed that the volatile compounds, including heptacosane, 1-octadecanesulphonyl chloride, and tetratetracontane, were induced under the NaCl stress treatment. Furthermore, the salt stress significantly improved the antioxidant capacity of the leaf extracts. These findings may provide insight into how H. cannabinus plants respond to salt stress and may help improve its medicinal value under salt stress.

Kenaf (Hibiscus cannabinus L.) is a valuable plant with a potential health benefit because of its extensive bioactive compounds. Leaf extracts of 33 kenaf genotypes were investigated for their polysaccharide, total phenolic, and flavonoid content. The antioxidant properties were evaluated by 2,2-Diphenyl-1-picrylhydrazyl (DPPH), 2,2′-azinobis (3-ethylbenzothiazoline-6-sulfonic acid (ABTS), and ferric reducing antioxidant potential (FRAP) assays. Antimicrobial capacity was also assessed against Staphylococcus aureus and Escherichia coli using a disc diffusion assay. The polysaccharide content varied from 6.45–16.12 mg glucose per g DW. Total phenolic and flavonoid content ranged from 6.03–21.15 mg GAE/g DW and 1.55–9.24 mg RE/g DW, respectively. Similarly, varied values in the range 20.55–79.99% of inhibition by DPPH, 56.28–88.30% of inhibition by ABTS and 1.26–5.08 mmol Fe²⁺/g DW by FRAP assays were obtained for antioxidants of the genotype extracts. Extracts from CS4 and CS2 genotypes had the highest antioxidant activities. Kenaf leaves exhibited antibacterial activity against Staphylococcus aureus and Escherichia coli. Strong correlation was found between antioxidant activity with polysaccharide (DPPH, r = 0.893; ABTS, r = 0.819; FRAP, r = 0.864) and total phenolic content (DPPH, r = 0.850; ABTS, r = 0.959; FRAP, r = 0.953). The results suggested that the kenaf leaves could be used as a natural antioxidants and antimicrobial in food industries.

Different parts of Corchorus olitorius and C. capsularis possess different antioxidant compounds. This study investigated the phytochemical components and antioxidant capacities of ultrasound-assisted extraction of different plant parts of both species using spectrophotometry at various phenological stages. Results also indicate that leaves, stems and roots of C. olitorius at various growth stages showed higher phytochemical components and antioxidant potential compared to C. capsularis. The phytochemical components from roots to leaves in C. olitorius including total polyphenol 0.97–11.11 mg GAE/g DW, total flavonoid 0.99–7.78 mg QE/g DW and total tannin 4.02–26.89 TA E/g DW, whereas C. capsularis total polyphenol 1.04–7.93 mg GAE/g DW, total flavonoid 0.77–5.5.92 mg QE/g DW and total tannin content 3.17–22.73 TA E/g DW. C. olitorius produced overall 22.23%, 13.61%, 12.24% higher total polyphenol, total flavonoid and total tannin, respectively compare to C. capsularis. Different parts extract also significantly affected antioxidant capacities including DPPH, ABTS, and FRAP activity with values of 22.03–79.46% inhibition, 10.84–104.10 μmol TE/g DW, and 10.84–104.10 μmol Fe^2+/g DW respectively for C. olitorius, while C. capsularis demonstrated 14.03–70.97% of DPPH inhibition, 9.16–95.60 μmol TE/g DW of ABTS and 5.31–71.82 μmol Fe^2+/g DW of FRAP activity. Moreover, leaves of the flowering stage, young stems and aged roots of both species displayed a higher content of phytochemical and antioxidant activities than other growth stages. A positive correlation between the phytochemical and antioxidant potential indicated that phenolic constituents solely affected antioxidant activity. Thus, this study established that the plant's parts and phenological growth stages significantly influence the concentration of phytoconstituents and antioxidant activities, and determine the harvesting stages of the different organs of C. olitorius and C. capsularis for considerable medicinal importance as folk and industry.

To address the demand for natural fibers, developing new varieties that are resistant to abiotic stress is necessary. The present study was designed to investigate the physiological and biochemical traits of three varieties of C. capularis (Y49, Y38, and Y1) and four varieties C. olitorius (T8, W57, M33, M18) under low temperature to identify the cold-tolerant varieties and elucidate the mechanisms involved in enhancing cold tolerance. Research findings revealed that the varieties Y49 and M33 exhibited the highest chlorophyll and carotenoid content. Biochemical profiles revealed that varieties Y49 and M33 were found to be able to withstand low-temperature stress by accumulating different enzymatic and non-enzymatic antioxidants, such as superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), ascorbate peroxidase (APx), glutathione (GSH), and phenolics, which participated in reducing the content of malondialdehyde (MDA) and hydrogen peroxide (H₂O₂) caused by low temperature. Osmolytes compounds, such as total soluble sugar, significantly increased in Y49 and M33; and proline content decreased in all varieties except Y49 and M33 after low-temperature exposure. The rise in these osmolytes molecules can be a defense mechanism for the jute’s osmotic readjustment to reduce the oxidative damage induced by low temperature. Furthermore, PCA and hierarchical cluster analysis distinguished the seven varieties into three separate groups. Results confirmed that group I (Y49 and M33 varieties) were low-temperature tolerant, group II (M18, W57) were intermediate, whereas III groups (Y38, T8, and Y1) were low temperature susceptible. PCA also explained 88.36% of the variance of raw data and clearly distinguished three groups that are similar to the cluster heat map. The study thus confirmed the tolerance of selected varieties that might be an efficient adaptation strategy and utilized them for establishing breeding programs for cold tolerance.