Phenylethanoid Glycosides from Houttuynia cordata and Their Hepatoprotective Activities

Duranta erecta Linn: A critical review on phytochemistry, traditional uses, pharmacology, and toxicity from phytopharmaceutical perspective

ETHNOPHARMACOLOGICAL RELEVANCE

Duranta erecta Linn. belonging to the Verbenaceae family is widely used in the traditional systems of medicines practiced in Bangladesh, India, Nigeria, the Philippines, and Brazil. The ethnomedicinal application as vermifuge, febrifuge, diuretic, anti-parasitic, and anti-malarial are well documented. D. erecta is also a significant source of phenylethanoid glycoside known as acteoside-a drug in clinical trials for IgA nephropathy patients.

AIM OF THIS REVIEW

This review aims to critically highlight the existing studies on D. erecta, including its botanical authentication, geographical distribution, ethnomedicinal uses, phytochemistry, and pharmacological properties. Critical discussion is focused on the overview and gap in knowledge for future research. Additionally, the clinical significance of its major secondary metabolite, i.e., acteoside, has also been discussed with emphasis on biosynthesis, distribution, pre-clinical, and clinical outcomes.

MATERIALS AND METHODS

Professional research data from 1963 to 2021 appeared in scholarly journals, and books were retrieved from scientific database platforms viz. Sci-Finder, PubMed, CNKI, Science Direct, Web of Science, Wiley, Google Scholar, Taylor and Francis, Springer, and Scopus. The chemical structures for all the phytomolecules were validated using Sci-finder and first-hand references. While plant name and synonyms were corroborated by "The Plant List" (www.theplantlist.org).

RESULTS

D. erecta and its key metabolite acteoside display various biological actions like antimalarial, antimicrobial, antioxidant, anticancer, antinephritic, hepatoprotective, neuroprotective, and antiviral properties. Acteoside literature analysis shows its presence in different stages of clinical trials for anti-nephritic, hepatoprotective, and osteoarthritic activity. The phytochemical review of D. erecta exhibited 64 compounds that have been isolated and identified from D. erecta, such as iridoid glycosides, phenylethanoid glycosides, flavonoids, steroids, phenolics, terpenoids, and saponins. The other significant secondary metabolites responsible for its medicinal properties are acteoside, durantol, pectolinaringenin, repenins, scutellarein, and repennoside.

CONCLUSION

Duranta erecta is one of the Verbenaceae plants, widely used in ethnomedicines having various phytochemicals with understandable pharmacological actions mainly confined at the crude extract level. However, further bioactivity-guided or fingerprint-assisted studies are required to validate the ethnomedicinal uses, concerning cellular and molecular mechanisms, quality standardization, and safety with respect to its bioactive constituent(s). Therefore, the present review identified the gap in the research on scientific validation of Duranta based ethnomedicines and may provide critical information for the development of phytopharmaceuticals/Phyto-cosmeceuticals.

Free radical scavenging activities of verbascoside and isoverbascoside from the leaves of Odontonema strictum (Acanthaceae)

The aqueous extract of the leaves of Odontonema strictum, a plant from tropical regions, is used by traditional physicians in Burkina Faso for its antihypertensive properties. Verbascoside and isoverbascoside, known phenylpropanoid glycosides with high solubility in water, have been isolated from the leaves. We evaluated their antioxidant properties in vitro by radical scavenging using 1,1-diphenyl-2-picrylhydrazyl (DPPH) and hydrogen peroxide (H₂O₂). Verbascoside and isoverbascoside demonstrated high levels of DPPH radical scavenging activity, with IC₅₀ values of 0.09 ± 0.03 μg/mL and 0.16 ± 0.07 μg/mL, respectively, compared to 0.05 ± 0.0 μg/mL for ascorbic acid as a control. These two phenylpropanoid glycosides were also more potent (2.6 ± 0.36 μg/mL and 3.0 ± 0.01 μg/mL) in scavenging H₂O₂ than the ascorbic acid control (4.1 ± 0.97 µg/mL). This is the first time that the antioxidant properties of verbascoside and isoverbascoside from O. strictum have been evaluated. These results can explain the use of this plant for hypertension in folk medicine.

Anti-hepatitis B virus activity and hepatoprotective effect of des(rhamnosyl) verbascoside from Lindernia ruellioides in vitro

Although clinically approved hepatitis B virus (HBV) polymerase inhibitors (lamivudine-3TC, entecavir, etc.) serve as effective therapeutics, the virus can easily generate resistance to them. Therefore, the treatment of HBV infection remains a public health problem. Numerous studies have shown that natural products have prospective anti-HBV activity. The purpose of this study was to isolate and extract des(rhamnosyl) verbascoside from Lindernia ruellioides (Colsm.) Pennell and explore its anti-HBV and hepatoprotective effects. Anti-HBV activity was evaluated in HepG2.2.15 cells, a human hepatocellular carcinoma cell line with HBV-stable infection, and its protective effect was evaluated in HL-7702 cells, a normal human liver cell line. HepG2.2.15 cells maintained normal growth morphology within the selected concentration range of des(rhamnosyl) verbascoside. It also inhibited the expression of HBV antigens and HBV DNA in a dose- and time-dependent manner in vitro. Further, western blot experiments showed that it could downregulate HBV X protein (HBx) expression in a dose-dependent manner. In the H₂ O₂ -induced hepatocyte injury model, the cell-survival rate of the HL-7702 cells with the highest drug dose reached 85.25%, which was significantly improved compared with that of the model group. Most of the cells returned to normal morphology, showing polygonal or fusiform structures. Thus, it may be stated that des(rhamnosyl) verbascoside exhibits anti-HBV activity and hepatoprotective effects in vitro and may exert an anti-HBV effect via antigen inhibition, HBV DNA secretion, and HBx protein expression.

Therapeutic potential of phenylethanoid glycosides: A systematic review

Phenylethanoid glycosides (PhGs) are generally water-soluble phenolic compounds that occur in many medicinal plants. Until June 2020, more than 572 PhGs have been isolated and identified. PhGs possess antibacterial, anticancer, antidiabetic, anti-inflammatory, antiobesity, antioxidant, antiviral, and neuroprotective properties. Despite these promising benefits, PhGs have failed to fulfill their therapeutic applications due to their poor bioavailability. The attempts to understand their metabolic pathways to improve their bioavailability are investigated. In this review article, we will first summarize the number of PhGs compounds which is not accurate in the literature. The latest information on the biological activities, structure-activity relationships, mechanisms, and especially the clinical applications of PhGs will be reviewed. The bioavailability of PhGs will be summarized and factors leading to the low bioavailability will be analyzed. Recent advances in methods such as bioenhancers and nanotechnology to improve the bioavailability of PhGs are also summarized. The existing scientific gaps of PhGs in knowledge are also discussed, highlighting research directions in the future.

Total phenylethanoid glycosides and magnoloside IafromMagnolia officinalisvar.bilobafruits inhibit ultraviolet B-induced phototoxicity and inflammation through MAPK/NF-κB signaling pathways

Magnolia officinalisvar.bilobais used as a traditional medicine in China and as a food additive in the United Kingdom and the European Union.

Houttuynoid M, an Anti-HSV Active Houttuynoid from Houttuynia cordata Featuring a Bis-houttuynin Chain Tethered to a Flavonoid Core

Houttuynoid M (1), a new houttuynoid, and the related known compound houttuynoid A (2) were isolated from Houttuynia cordata. Their structures were defined using NMR data analysis, HR-MSⁿ experiment, and chemical derivatization. Houttuynoid M is the first example of a houttuynoid with a bis-houttuynin chain tethered to a flavonoid core. A putative biosynthetic pathway of houttuynoid M (1) is proposed. The anti-herpes simplex virus (anti-HSV) activities of 1 and 2 (IC₅₀ values of 17.72 and 12.42 μM, respectively) were evaluated using a plaque formation assay with acyclovir as the positive control.