Phytobioactive compounds as therapeutic agents for human diseases: A review

Abstract

Phytobioactive compounds are plant secondary metabolites and bioactive compounds abundantly present in medicinal plants and have remarkable therapeutic potential. Oxidative stress and antibiotic resistance are major causes of present-day ailments such as diabetes, atherosclerosis, cardiovascular disorders, cancer, and inflammation. The data for this review were collected from Google Scholar, PubMed, Directory of Open Access Journals (DOAJ), and Science Direct by using keywords: "Medicinal plants, Phytobioactive compounds, Polyphenols, Alkaloids, Carotenoids etc." Several studies have reported the pharmacological and therapeutic potential of the phytobioactives. Polyphenols, alkaloids, terpenes, and polysaccharides isolated from medicinal plants showed remarkable antioxidant, anticancer, cytotoxic, anti-inflammatory, cardioprotective, hepatoprotective, immunomodulatory, neuroprotective, and antidiabetic activities. This literature review was planned to provide comprehensive insight into the biopharmacological and therapeutic potential of phytobioactive compounds. The techniques used for the extraction and isolation of phytobioactive compounds, and bioassays required for their biological activities such as antioxidant, antimicrobial, anti-inflammatory, and cytotoxic activities, have been discussed. Characterization techniques for the structural elucidation of phytobioactive compounds such as HPLC, TLC, FTIR, GC-MS/MS, and NMR have also been discussed. This review concludes that phytobioactive compounds may be used as potential alternative to synthetic compounds as therapeutic agents for the treatment of various diseases.

Keywords: alkaloids; medicinal plants; phytobioactive compounds; polyphenols; terpenoids.

FIGURE 1

Classification of phytobioactive compounds.

FIGURE 2

Overview of the therapeutic potential of phytobioactive compounds.

FIGURE 3

Schematic mechanism of phytobioactive compounds in treating type 2 diabetes.

FIGURE 4

Molecular mechanism of the anticancer activity of polyphenolic compounds. 5‐LOX, lipoxygenase; AP‐1, activator protein‐1; CDK, cyclin‐dependent kinase; COX2, cyclooxygenase 2; CYP, cytochrome P; GCL, glutamate cysteine ligase; GPX, Glutathione peroxidase; GST, glutathione S‐transferase; HIF‐1 α, hypoxia‐inducible factor 1α; HO‐1, hemeoxygenase‐1; IKK, IκB kinase; iNOS, inducible nitric oxide synthase; JNK, c‐Jun N‐terminal Kinase; MAPK, mitogen‐activated protein kinases; MMP9, matrix metalloprotease‐9; NF‐ κB, nuclear factor‐κB; NQO1, nicotinamide adenine dinucleotide phosphate, quinone oxidoreductase; Nrf2, NF‐E2‐related factor 2; PDGF, platelet‐derived growth factor; PDGFR, PDGF receptor; PKC, protein kinase C; QR, quinone reductase; VEGF, vascular endothelial growth factor; VEGFR, VEGF receptor; γGCS, γ‐glutamylcysteine synthetase.

FIGURE 5

Possible molecular mechanism of anti‐inflammatory activity of plant terpenes.

FIGURE 6

Possible action mechanism of plant polysaccharides as antioxidant, anti‐inflammatory, antidiabetic, and immunomodulatory agents. Plant polysaccharides increase the endogenously produced antioxidant enzymes like catalase and superoxide dismutase levels, whereas significantly reduce ROS‐induced free radicals, which are responsible for the destruction of important biomolecules found in body tissues that lead to apoptosis. These polysaccharides are primarily involved in the downregulation of toll‐like receptor 4 (TLR‐4) and NF‐κB, a nuclear transcription factor involved in inflammatory diseases by triggering the inducible NO synthase, TNFα, IL‐6, and IL‐1β. Antidiabetic activity of plant polysaccharides has been shown through various mechanisms including antioxidative and anti‐inflammatory properties by alleviating β‐cell dysfunctioning, increasing insulin secretion, and inhibiting the α‐amylase and α‐glucosidase activity to improve glucose metabolism. Plant polysaccharides exhibit immune‐modulatory activity by inducing ROS and cell proliferation and increasing cytokines and macrophages phagocytosis.