No abstract

Plants have been extensively studied since ancient times and numerous important chemical constituents with tremendous therapeutic potential are identified. Attacks of microorganisms including viruses and bacteria can be counteracted with an efficient immune system and therefore, stimulation of body’s defense mechanism against infections has been proven to be an effective approach. Polysaccharides, terpenoids, flavonoids, alkaloids, glycosides, and lactones are the important phytochemicals, reported to be primarily responsible for immunomodulation activity of the plants. These phytochemicals may act as lead molecules for the development of safe and effective immunomodulators as potential remedies for the prevention and cure of viral diseases. Natural products are known to primarily modulate the immune system in nonspecific ways. A number of plant-based principles have been identified and isolated with potential immunomodulation activity which justify their use in traditional folklore medicine and can form the basis of further specified research. The aim of the current review is to describe and highlight the immunomodulation potential of certain plants along with their bioactive chemical constituents. Relevant literatures of recent years were searched from commonly employed scientific databases on the basis of their ethnopharmacological use. Most of the plants displaying considerable immunomodulation activity are summarized along with their possible mechanisms. These discussions shall hopefully elicit the attention of researchers and encourage further studies on these plant-based immunomodulation products as potential therapy for the management of infectious diseases, including viral ones such as COVID-19.

Salvadora persica L. (Salvadoraceae) is an evergreen shrub growing in the Middle East, Africa, and Southern Asia. It is traditionally known as “miswak” and used as toothbrushes and for the treatment of toothache, gum diseases, boils, chest infection, gonorrhea, headache, spleen troubles, stomachache, and ulcers. To the best of our knowledge, this is the first study aimed at conducting phytochemical, cytotoxic, and antimicrobial investigations of the fruits (berries) of S. persica collected from the Jazan region of Saudi Arabia. Analysis of the ethanol extract of S. persica fruits using GC-MS showed the presence of six esters (20.71%), seven alkanes (15.47%), tetracosamethyl-cyclododecasiloxane (9.91%), eicosamethyl-cyclodecasiloxane (7.27%), and 1-monolinoleoylglycerol (5.17%). The predominant constituents were acetyl dasycarpidan-1-methanol (10.47%), tetracosamethyl-cyclododecasiloxane (9.91%), eicosamethyl-cyclodecasiloxane (7.27%), and 1-monolinoleoylglycerol (5.17%). The petroleum ether extract of the fruits contained mainly eicosamethyl-cyclodecasiloxane (23.81%), 1-monolinoleoylglycerol (11.78%), (Z,Z,Z)-9,12,15-octadecatrienoic acid ethyl ester derivative (10.56%), and tetracosamethyl-cyclododecasiloxane (9.91%). The cytotoxic properties of the ethanol extract were investigated by MTT assay against the breast MCF7, ovary A2780, and colon HT29 cells. The fruit extract of S. persica was selective against the ovarian and colon cancer cells compared to normal fibroblast cells (MRC5) as it showed IC50 values 17.50, 8.35, and 5.12, against MCF7, A2780, and HT29 cells, respectively. Interestingly, the fruit extract was also found to possess selective antimicrobial activity for Streptococcus mutans isolates with minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) values of 3.12 and 6.25 mg/mL, respectively. Interestingly, it was found to be ineffective against other Gram-positive as well as Gram-negative microorganisms. This study provides insight into the bioactive components present in the fruits of the plant that can be utilized for its cytotoxic and antimicrobial properties.

Viral infections and associated diseases are responsible for a substantial number of mortality and public health problems around the world. Each year, infectious diseases kill 3.5 million people worldwide. The current pandemic caused by COVID-19 has become the greatest health hazard to people in their lifetime. There are many antiviral drugs and vaccines available against viruses, but they have many disadvantages, too. There are numerous side effects for conventional drugs, and active mutation also creates drug resistance against various viruses. This has led scientists to search herbs as a source for the discovery of more efficient new antivirals. According to the World Health Organization (WHO), 65% of the world population is in the practice of using plants and herbs as part of treatment modality. Additionally, plants have an advantage in drug discovery based on their long-term use by humans, and a reduced toxicity and abundance of bioactive compounds can be expected as a result. In this review, we have highlighted the important viruses, their drug targets, and their replication cycle. We provide in-depth and insightful information about the most favorable plant extracts and their derived phytochemicals against viral targets. Our major conclusion is that plant extracts and their isolated pure compounds are essential sources for the current viral infections and useful for future challenges.

Two new compounds, 14-methyl stigmast-9(11)-en-3alpha-ol-3beta-D-glucopyranoside (1) and cholest-11-en-3beta, 6beta, 7alpha, 22beta-tetraol-24-one-3beta-palmitoleate (2), along with the known compound beta-sitosteryl-3beta-D-glucopyranosyl-6'-linoleiate (3), were isolated from the methanolic extract of rice (Oryza sativa) hulls. The structures of the two new compounds were elucidated using one- and two-dimensional NMR in combination with IR, EI/MS, FAB/MS, HR-EI/MS and HR-FAB/MS. In bioassays with blue-green algae, Microcystis aeruginosa UTEX 2388 and duckweed, Lemna paucicostata Hegelm 381, the efficacy of bioactivity of the two new compounds linearly increased as the concentration increased from 0.3 to 300 IgM. Compared with momilactone A, compounds 1 and 2 showed similar and higher inhibitory activities against the growth of M. aeruginosa at a concentration of 300 microM. However, compound 2 was similar to momilactone A in inhibiting L. paucicostata growth at a concentration of 300 microM. As a result, compound 2 appears to have a strong potential for the environmentally friendly control of weed and algae that are harmful to water-logged rice.