Microbial resistance and other emerging health risk problems related to the side effects of synthetic drugs are the major factors that result in the research regarding natural products. Fruits, leaves, seeds, and oils-based phyto-constituents are the most important source of pharmaceutical products. Plant extract chemistry depends largely on species, plant components, solvent utilized, and extraction technique. This study was aimed to compare the ethanolic extracts of a mangrove plant, i.e., Avicennia marina (1E: Lower half of A. marina‘s pneumatophores, 2E: A. marina‘s leaves, 3E: Upper half of A. marina‘s pneumatophores, and 4E: A. marina‘s shoots), with non-mangrove plants, i.e., Phragmites australis (5E: P. australis‘s shoot), and Moringa oleifera (6E: M. oleifera‘s leaves) for their antimicrobial activities, total phenolic contents, antioxidant activity, and cytotoxicity potential. The antimicrobial activity assays were performed on gram-positive bacteria (i.e., Bacillus subtilis and Staphylococcus aureus), gram-negative bacteria (i.e., Escherichia coli, and Pseudomonas aeruginosa), and fungi (i.e., Aspergillus niger, Candida albicans, and Rhizopus spp.). We estimated antioxidant activity by TAC, DPPH, and FRAP assays, and the cytotoxicity was evaluated by MTT assay. The results of antimicrobial activities revealed that B. subtilis was the most sensitive to the tested plant extracts compared to S. aureus, while it only showed sensitivity to 6E and Imipenem. 5E and 6E showed statistically similar results against P. aeruginosa as compared to Ceftazidime. E. coli was the most resistant bacteria against tested plant extracts. Among the tested plant extracts, maximum inhibition activity was observed by 6E against A. niger (22 ± 0.57 mm), which was statistically similar to the response of 6E against C. albicans and 3E against Rhizopus spp. 2E did not show any activity against tested fungi. We found that 6E (208.54 ± 1.92 mg g⁻¹) contains maximum phenolic contents followed by 1E (159.42 ± 3.22 mg g⁻¹), 5E (131.08 ± 3.10 mg g⁻¹), 4E (i.e., 72.41 ± 2.96 mg g⁻¹), 3E (67.41 ± 1.68 mg g⁻¹), and 2E (48.72 ± 1.71 mg g⁻¹). The results depict a significant positive correlation between the phenolic contents and the antioxidant activities. As a result, phenolic content may be a natural antioxidant source.

Halotolerant, plant growth-promoting rhizobacteria (PGPR) are known to alleviate plant growth under abiotic stresses, especially those isolated from saline arid soils. In this study, 66 bacterial isolates, obtained from various habitats in Saudi Arabia, were characterized for their plant growth-promoting (PGP) traits, and screened for heat and salt stress resilience. Finally, selected halotolerant PGPR strains were assessed for their potential to improve maize (Zea mays L.) growth under salinity stress using in vitro assays. Our results indicated that many isolates possessed key PGP traits such ACC deaminase, N-fixation, and phytohormone production. Additionally, several isolates were able to tolerate high temperatures, and 20 bacterial isolates were classified as halotolerant. Furthermore, among the isolates, Pseudomonas soyae (R600), Bacillus haynesii (SFO145), Salinicola halophilus (SFO075), and Staphylococcus petrasii (SFO132) significantly enhanced various maize growth parameters under salt stress conditions when compared to uninoculated plants. These halotolerant PGPR are good candidates to be explored as bioinoculants for sustainable agriculture under saline arid soil conditions.

Industrial activities are associated with various heavy metals (HMs) being emitted into the environment, which may pose a threat to humans and animals. The rapid increase in an industrial activity in major cities in Saudi Arabia (SA) has raised concerns regarding the accumulation of HMs in the environment. The aim of this study is to assess the accumulation of HMs in soil and native plants in an industrial environment. We collected 36 surface soil samples and 12 plant species from 12 sites in an industrial city in central SA. The results showed that the HMs content in the soil followed a descending order of (Fe > Ni > Zn > Pb > Cu> Cr > Cd). The enrichment factor (EF) of HMs in the soil ranged from 0.20 to 7336. Up to 100%, 16.6%, and 6.2% of soil samples were extremely highly enriched with Cd, Ni, and Pb, respectively. Plant species Cyperus laevigatus accumulate Cd, Pb, and Ni. Citrullus colocynthis accumulate Cd and Pb in significantly (p < 0.001) higher amounts than other studied species. The Pollution Load Index (PLI) values for the 12 sites ranged from 0.52–1.33 with S5 and S2 PLI >1.0 indicating progressive deterioration of these sites. The Bioaccumulation Factor (BF) ranged from 0.04–2.76 and revealed that some plant species may be candidates for phytoextraction potential. The most promising plant species for phytoextraction and remediation were annuals or perennials such as Malva parviflora, Sisymbrium irio and Citrullus colocynthis, especially for Cr and Cu. This study suggests that these native plant species may be useful for phytoremediation in the area.

Fifty-four groundwater samples were collected from Hamra Alasad in Al-Madinah City. The chemical and microbial characteristics of the samples were analyzed and compared with their respective standards. The results revealed that 90.7% of the samples showed higher amounts of NO₃. However, 59.3% of the samples were found unfit for irrigation purposes due to a high salinity hazard. Most of the groundwater samples were highly saline, yet no sodicity hazards were anticipated as predicted by sodium adsorption ratio (SAR). Generally, the soluble cations and anions, dissolved salts, boron, and NO₃⁻ exceeded the maximum permissible limits for drinking water in most of the samples; however, Pb, Cd, As, Zn, Cu, Ni, Co, Fe, Mn, and Cr were within the permissible limits. Furthermore, 42.6%, 24.1%, 18.5%, 14.8%, 1.9%, and 37.0% of the samples were infected by a total coliforms group, fecal coliform, Escherichia coli, Staphylococcus sp., Salmonella sp., and Shigilla sp., respectively. The water quality index revealed that 3.7% of the samples were good for drinking (class II), and 9.3% were very poor (class IV). The remaining samples were unfit for drinking (class V) due to high salinity and/or microbial contamination. Durov and Piper diagrams revealed that the majority of water samples were of the calcium sulfate–chloride type. Overall, 87% of water samples were inappropriate for drinking purposes, while 77.8% were unsuitable for irrigation.

The objective of this study was to compare and assess the quality and study the hydrochemistry of groundwater in the Al-Baha and Al-Qassim areas, representing the Arabian Shield and Arabian Shelf, respectively, of the Arabian Peninsula. The chemical and microbiological constituents of the groundwaters of the two sites were acquired and compared. The Al-Baha analyses indicated that the underground water near urban area is subject to contamination by E. coli and nitrate. However, the dissolved salts and soluble ions were at an acceptable level according to WHO standards. In Al-Qassim, 77% of the studied groundwater samples were inappropriate for drinking because of high salinity; however, 60% had slight to moderate salinity hazard for use in irrigation. At both regions, trace elements were found to be within acceptable limits for irrigation and drinking. Piper, Schoeller, and Durov diagrams showed that the majority of the investigated groundwaters in Al-Baha were calcium–magnesium, chloride–sulfate water type. However, 51% of the studied waters in Al-Qassim were sodium, chloride, sulfate water type. The geology of Al-Baha is comprised of gypsum, anhydride, and dolomite. The geology of Al-Qassim is dominantly comprised of halite. The saturation index indicated that the Al-Baha groundwaters are undersaturated with respect to halite, gypsum, and anhydrite; however, the groundwaters of Al-Qassim are undersaturated with respect to halite. The approach utilized in this investigation could be useful in similar environments worldwide.

Rapid industrialization has resulted in the release and subsequent accumulation of heavy metals (HMs) in various environmental matrices, which poses serious health threats globally. Utilizing native plant species to extract such HMs from soil may be an efficient and cost-effective remediation approach. Thus, HM accumulation in soil and native plant species in the industrial area of Al-Qassim province, Saudi Arabia, was investigated in this study, and the phytoremediation potential of the native plant species was assessed. Briefly, 30 surface soil samples and 10 native plants samples were collected from 10 different locations in the studied area. Soil samples were analyzed for physiochemical characteristics and HM contents, while the plant samples were digested and HM concentrations were determined. The results showed that Fe was highest in concentration from soil samples (3900–19,600 mg kg⁻¹), followed by Mn, Zn, Ni, Pb, Cr, Cu, and Cd. Similarly, Fe concentration was also higher in plant samples (432 mg kg⁻¹), followed by Mn (70.2 mg kg⁻¹) and Zn (38.1 mg kg⁻¹). Enrichment factor revealed that 90% of the samples were extremely enriched with Cd, while 20% were highly enriched with Pb. Similarly, contamination factor (5.0–46.9) was also the highest for Cd. Higher bioaccumulation factor (>1) of Phrgmites australis and Chenopodium marale for Cd and Cu, Chenopodium album, Lactuca serviola, and Chenopodium marale for Cu, and Pulicaria crispa for Mn suggested that these native plants can be effectively used for phytoremediation of HMs in soil.