Respiratory inflammation is caused by an air-mediated disease induced by polluted air, smoke, bacteria, and viruses. The COVID-19 pandemic is also a kind of respiratory disease, induced by a virus causing a serious effect on the lungs, bronchioles, and pharynges that results in oxygen deficiency. Extensive research has been conducted to find out the potent natural products that help to prevent, treat, and manage respiratory diseases. Traditionally, wider floras were reported to be used, such as Morus alba, Artemisia indica, Azadirachta indica, Calotropis gigantea, but only some of the potent compounds from some of the plants have been scientifically validated. Plant-derived natural products such as colchicine, zingerone, forsythiaside A, mangiferin, glycyrrhizin, curcumin, and many other compounds are found to have a promising effect on treating and managing respiratory inflammation. In this review, current clinically approved drugs along with the efficacy and side effects have been studied. The study also focuses on the traditional uses of medicinal plants on reducing respiratory complications and their bioactive phytoconstituents. The pharmacological evidence of lowering respiratory complications by plant-derived natural products has been critically studied with detailed mechanism and action. However, the scientific validation of such compounds requires clinical study and evidence on animal and human models to replace modern commercial medicine.

α-Amylase is an enzyme involved in the breaking down of large insoluble starch molecules into smaller soluble glucose molecules. Catunaregam spinosa (Thunb.) Tirveng. (syn. Randia dumetorum (Retz.) Lam., Family: Rubiaceace) has been used as traditional medicine for the treatment of gastrointestinal problems, skin diseases, and diabetes. In this context, we studied the in vitro α-amylase inhibiting properties of methanol extracts of leaves and bark of C. spinosa. The methanol extract of bark was further fractionated into hexane, dichloromethane and ethyl acetate, and water-soluble fractions, and their α-amylase inhibitory activity was evaluated. In silico molecular docking and ADMET analysis of several compounds previously reported from the bark of C. spinosa were also performed. The in vitro α-amylase inhibition activity assay of the dichloromethane fraction of extract of bark (IC50: 77.17 ± 1.75  μg/mL) was more potent as compared to hexane and ethyl acetate fractions. The in silico molecular docking study showed that previously reported compounds from the stem bark such as balanophonin, catunaregin, β-sitosterol, and medioresinol were bounded well with the active catalytic residue of porcine pancreatic α-amylase indicating better inhibition. The ADMET analysis showed the possible drug-likeness and structure-activity relationship of selected compounds. These compounds should be studied further for their potential α-amylase inhibition in animal models.

Catunaregam spinosa (Thunb.) Tirveng. (Syn. Randia dumetorum (Retz.) Lam.), belonging to the Rubiaceae family, is distributed in south Asian countries. It is used as a traditional medicine to treat gastrointestinal and hepatic problems and as an anti-inflammatory and antimicrobial agent. The main aim of this review is to collect and analyze the available scientific information on traditional uses, phytochemistry, and pharmacological activities of C. spinosa. The scientific information related to C. spinosa was collected from various resources and databases such as SciFinder, Scopus, PubMed, and other databases. C. spinosa was found to be an important crude drug of the traditional medicinal systems such as Ayurveda. It was found to be used by the people of India as an alternative medicine, while the fruit of this plant was found to be used in dietary regimens as well. Active phytochemicals such as catunarosides, randianin, and several other saponins and triterpenoids possess various pharmacological activities such as anti-inflammatory, hepatoprotective, antibacterial, and immunomodulatory activities. Many studies have been performed to isolate the active compounds; however, there is a need for more activity-guided isolation studies. Various in vitro studies showed promising results but there are not many studies related to mechanism of actions using animal models. Hence, future studies on C. spinosa should focus on correlating the traditional uses with active phytoconstituents and modern pharmacological activities.