Phyllanflexoid C: first example of phenylacetylene-bearing 18-nor-diterpenoid glycoside from the roots of Phyllanthus flexuosus

A Comprehensive Review of the Classification, Sources, Phytochemistry, and Pharmacology of Norditerpenes

Norditerpenes are considered to be a common and widely studied class of bioactive compounds in plants, exhibiting a wide array of complex and diverse structural types and originating from various sources. Based on the number of carbons, norditerpenes can be categorized into C19, C18, C17, and C16 compounds. Up to now, 557 norditerpenes and their derivatives have been found in studies published between 2010 and 2023, distributed in 51 families and 132 species, with the largest number in Lamiaceae, Euphorbiaceae, and Cephalotaxaceae. These norditerpenes display versatile biological activities, including anti-tumor, anti-inflammatory, antimicrobial, and antioxidant properties, as well as inhibitory effects against HIV and α-glucosidase, and can be considered as an important source of treatment for a variety of diseases that had a high commercial value. This review provides a comprehensive summary of the plant sources, chemical structures, and biological activities of norditerpenes derived from natural sources, serving as a valuable reference for further research development and application in this field.

Anti-inflammatory ent-cleistanthane-type diterpenoids from Phyllanthus rheophyticus

A bioactivity-guided isolation from the aerial parts of Phyllanthus rheophyticus obtained 17 undescribed ent-cleistanthane-type diterpenoids, namely phyllarheophols A-Q, as well as 12 known analogs. Their structures were characterized by a combination of spectroscopic data interpretation, single-crystal X-ray diffraction and ECD analysis. The anti-inflammatory activities of these compounds were evaluated by measuring their inhibitory effects on NO production in LPS-stimulated RAW264.7 macrophages, and their preliminary structure-activity relationships were also discussed. Further study showed that promising compounds phyllarheophol D and phyacioid B significantly suppressed the expressions of cytokines and nitric oxide synthase through the NF-κB signaling pathway.

New ent-Kaurane and cleistanthane diterpenoids with potential cytotoxicity from Phyllanthus acidus (L.) Skeels

Six diterpenoids including three ent-kauranes (1-2, 4) and three cleistanthanes (3, 5-6) were isolated from the roots and stems of Phyllanthus acidus (L.) Skeels. Of them, (16S)-ent-16,17,18-tri-hydroxy-19-nor-kaur-4-en-3-one (1), phyllanthone A (2), and 6-hydroxycleistanthol (3) are new compounds, while the ent-kaurane diterpenoids were reported from the titled plant for the first time. Their structures were elucidated on the basis of the extensive spectroscopic analyses. Compounds 2 and 4-6 displayed cytotoxic potential with IC₅₀ values ranging from 1.96 to 29.15 μM. They also showed moderate anti-inflammatory activities (IC₅₀ = 6.30-12.05 μM). Particularly, the new ent-kaurane 2 displayed cytotoxic potential against HL-60 (IC₅₀ = 2.00 μM) and MCF-7 (IC₅₀ = 3.55 μM) cells, and anti-inflammatory activity (IC₅₀ = 6.47 μM).

Phyllaciduloids E and F, two new cleistanthane diterpenoids from the leaves of Phyllanthus acidus

Phyllaciduloids E (1) and F (2), two new cleistanthane diterpenoids, were isolated from the leaves of Phyllanthus acidus (L.) Skeels (Phyllanthaceae). Their planar structures were established by spectroscopic analysis and comparison with literature values. The relative configurations of phyllaciduloids E and F were confirmed by DFT-NMR chemical shift calculations and subsequent CP3 probability methods. Phyllaciduloids E and F were evaluated for their cytotoxicity. However, no significant activities were detected at concentrations up to 40 μM.

Phyllanacidins A-C, three new cleistanthane diterpenoids from Phyllanthus acidus and their cytotoxicities

Phytochemical investigation on the nonpolar extracts of P. acidus leaves afforded three new cleistanthane diterpenoids, named phyllanacidins A-C (1-3), in addition to three known ones (4-6). Among them, compounds 2 and 3 represent the first examples of 17-nor cleistanthane diterpenoids. Their structures including absolute configurations were elucidated on the basis of extensive spectroscopic data and single crystal X-ray diffraction analysis. All the isolated cleistanthane diterpenoids were evaluated for their cytotoxic activities against five human cancer cell lines. Compounds 4-6 exhibited moderate cytotoxicity with IC₅₀ values ranging from 16.11 to 30.82 μM.

A New Purine Derivative from the Roots of Phyllanthus flexuosus

A new purine derivative, 1-methyl-3-isopentenylisoguanine (1), together with six known compounds (2-7), was isolated from the roots of Phyllanthus flexuosus. The newly isolated structure was established by means of extensive spectroscopic analysis and single-crystal X-ray diffraction experiment. All isolates were evaluated for their in vitro cytotoxicities against two human hepatocellular carcinoma cell lines (HepG2 and SMMC-7721) by CCK-8 assays. Among them, three cleistanthane diterpenes (2–4) exhibited different levels of cytotoxicities against these cells with IC50 values ranging from 27.34 to 53.28 μM. Furthermore, acetylcholinesterase inhibitory effect for the new purine derivative was also assessed.

Enantiomeric Lignans and Neolignans from Phyllanthus glaucus: Enantioseparation and Their Absolute Configurations

Eight pairs of enantiomeric neolignans, norlignans, and sesquineolignans (1a/1b–8a/8b), together with five known neolignans (9a/9b and 10–12), have been isolated from 70% acetone extract of the whole plants of Phyllanthus glaucus Wall. (Euphorbiaceae). The racemic or partial racemic mixtures were successfully separated by chiral HPLC using different types of chiral columns with various mobile phases. Their structures were elucidated on the basis of extensive spectroscopic data. The absolute configurations of 2a/2b were determined by computational analysis of their electronic circular dichroism (ECD) spectrum, and the absolute configurations of other isolates were ascertained by comparing their experimental ECD spectra and optical rotation values with those of structure-relevant compounds reported in literatures. Compounds 4a/4b featured unique sesquineolignan skeletons with a novel 7-4′-epoxy-8′-8′′/7′-2′′ scaffold, consisting of an aryltetrahydronaphthalene and a dihydrobenzofuran moiety. The planar structures of compounds 2, 3, 7, and 8 were documented previously; however, their absolute configurations were established for the first time in this study. The antioxidant activities of 1a/1b–8a/8b were evaluated using DPPH free radical scavenging assay, and the results demonstrated that compounds 1b and 3b showed potent DPPH radical scavenging activities with IC₅₀ values of 5.987 ± 1.212 and 9.641 ± 0.865 μg/mL, respectively.

The Genus Phyllanthus: An Ethnopharmacological, Phytochemical, and Pharmacological Review

The plants of the genus Phyllanthus (Euphorbiaceae) have been used as traditional medicinal materials for a long time in China, India, Brazil, and the Southeast Asian countries. They can be used for the treatment of digestive disease, jaundice, and renal calculus. This review discusses the ethnopharmacological, phytochemical, and pharmacological studies of Phyllanthus over the past few decades. More than 510 compounds have been isolated, the majority of which are lignins, triterpenoids, flavonoids, and tannins. The researches of their remarkable antiviral, antioxidant, antidiabetic, and anticancer activities have become hot topics. More pharmacological screenings and phytochemical investigations are required to support the traditional uses and develop leading compounds.

Anti-hepatitis B virus activities and absolute configurations of sesquiterpenoid glycosides from Phyllanthus emblica

During the process exploring anti-viral compounds from Phyllanthus species, eight new highly oxygenated bisabolane sesquiterpenoid glycoside phyllaemblicins G1–G8 (1–8) were isolated from Phyllanthus emblica, along with three known compounds, phyllaemblicin F (9), phyllaemblic acid (10) and glochicoccin D (11). Phyllaemblicin G2 (2), bearing a tricyclo [3.1.1.1] oxygen bridge ring system, is an unusual sesquiterpenoid glycoside, while phyllaemblicins G6–G8 (6–8) are dimeric sesquiterpenoid glycosides with two norbisabolane units connecting through a disaccharide. All the structures were elucidated by the extensive analysis of HRMS and NMR data. The relative configuration of phyllaemblicin G2 was constructed based on heteronuclear coupling constants measurement, and the absolute configurations for all new compounds were established by calculated electronic circular dichroism (ECD) using time dependent density functional theory. The sesquiterpenoid glycoside dimers 6–9 displayed potential anti-hepatitis B virus (HBV) activities, especially for the new compound 6 with IC50 of 8.53 ± 0.97 and 5.68 ± 1.75 μM towards the HBV surface antigen (HBsAg) and HBV excreted antigen (HBeAg) secretion, respectively.

Stereochemistry of cleistanthane diterpenoid glucosides from Phyllanthus emblica

Theoretical calculated electronic circular dichroism and Mosher’s method were applied to elucidate the stereochemistry of cleistanthane diterpenoids.

Diterpenoids of terrestrial origin

This review covers the isolation and chemistry of diterpenoids from terrestrial as opposed to marine sources and includes labdanes, clerodanes, pimaranes, abietanes, kauranes, gibberellins, cembranes and their cyclization products. The literature from January to December 2013 is reviewed.

Highly Oxygenated Limonoids and Lignans from Phyllanthus flexuosus

ABSTRACT

Two new highly oxygenated limonoids, flexuosoids A (1) and B (2), and three new arylnaphthalene lignan glycosides, phyllanthusmins D-F (3-5), were isolated from the roots of Phyllanthus flexuosus, in addition to three known lignans, phyllanthusmin C, arabelline, and (+)-diasyringaresinol. Their structures were elucidated on the basis of detailed spectroscopic analysis and chemical methods. Compounds 1 and 2, two new decaoxygenated limonoids with a C-19/29 lactol bridge and heptaoxygenated substituents at C-1, C-2, C-3, C-7, C-11, C-17, and C-30, represent the second example of limonoids in the Euphorbiaceae family. Most of the isolates were tested for their antifeedant, anti-herpes simplex virus 1, and cytotoxic activities. The new limonoids 1 and 2 showed promising antifeedant activity against the beet army worm (Spodoptera exigua) with EC50 values of 25.1 and 17.3 μg/cm(2), respectively. In addition, both of them displayed moderate cytotoxicity against the ECA109 human esophagus cancer cell line, along with the known lignan glycoside, phyllanthusmin C, with the IC50 values of 11.5 (1), 8.5 (2), and 7.8 (phyllanthusmin C) μM, respectively.

GRAPHICAL ABSTRACT

Two new highly oxygenated limonoids, flexuosoids A (1) and B (2), and three new arylnaphthalene lignan glycosides, phyllanthusmins D-F (3-5), were isolated from the roots of Phyllanthus flexuosus, along with three known lignans. Flexuosoids A (1) and B (2) showed promising antifeedant activity against the beet army worm (Spodoptera exigua) with EC50 values of 25.1 and 17.3 μg/cm(2), respectively. In addition, both of them and the known lignan glycoside, phyllanthusmin C, displayed moderate cytotoxicity against the ECA109 human esophagus cancer cell line, with the IC50 values of 11.5, 8.5, and 7.8 μM, respectively.