Antioxidative activity of diarylheptanoids from the bark of black alder (Alnus glutinosa) and their interaction with anticancer drugs

Activation of JNK and p38 in MCF-7 Cells and the In Vitro Anticancer Activity of Alnus hirsuta Extract

JNK and p38 are important mitogen-activated protein kinases (MAPKs) that respond to stress stimuli. The stress-activated MAPKs associated with apoptotic cell death play vital roles in mammalian cells. Alnus hirsuta, which contains abundant diarylheptanoids derivatives, is a valuable medicinal plant. The CHCl3 extract (AHC) containing platyphyllenone (1) and platyphyllone (3) as main compounds showed in vitro anticancer effects. We report the biological activities of A. hirsuta extract associated with the regulation of apoptosis and JNK and p38 in MCF-7 breast cancer cells. Levels of phospho-JNK and phospho-p38 by AHC treatment were evaluated by enzyme-linked immunosorbent assay (ELISA). ROS production, apoptotic effect, and DNA contents of the cells were measured by flow cytometry. The two diarylheptanoids 1 and 3 and the AHC extract exhibited cytotoxic effects on MCF-7 cells in MTT assay, with IC50 values of 18.1, 46.9, 260.0 μg/mL, respectively. AHC induced ROS generation and elevated the endogenous levels of phospho-JNK and phospho-p38. AHC resulted in apoptosis and cell cycle arrest. We suggest that the antitumor effect of A. hirsuta extract is achieved by apoptosis promotion and cell cycle arrest mediated by the activation of JNK and p38 signaling pathway via ROS generation.

Sulfocoumarins, specific carbonic anhydrase IX and XII inhibitors, interact with cancer multidrug resistant phenotype through pH regulation and reverse P-glycoprotein mediated resistance

New 6-triazolyl-substituted sulfocoumarins were described as potent inhibitors of the transmembrane human carbonic anhydrase isoforms, CAIX and CAXII. These membrane associated enzymes that maintain pH and CO₂ homeostasis are involved in cancer progression, invasion, and resistance to therapy. Recently, it was shown that CAXII expression associates with the expression of P-glycoprotein in multidrug resistant cancer cells. CAXII regulates P-glycoprotein activity by maintaining high intracellular pHi. In this study, the activity of three new sulfocoumarins was evaluated in three sensitive and corresponding multidrug resistant cancer cell lines with increased P-glycoprotein expression (non-small cell lung carcinoma, colorectal carcinoma and glioblastoma). Compound 3 showed the highest potential for cancer cell growth inhibition in all tested cell lines. Flow cytometric analyses showed that compound 3 induced intracellular acidification, cell cycle arrest in G₂/M phase and necrosis in non-small cell lung carcinoma cells. Compound 3 demonstrated irreversible, concentration- and time-dependent inhibition of P-glycoprotein activity in multidrug resistant non-small cell lung carcinoma cells. The suppression of P-glycoprotein activity was accompanied with increased P-glycoprotein expression suggesting a compensatory mechanism of multidrug resistant cancer cells. In addition, compound 3 was able to sensitize multidrug resistant non-small cell lung carcinoma cells to doxorubicin. Overall, results imply that compound 3 has multidrug resistance modulating effect through intracellular acidification and subsequent inhibition of P-glycoprotein activity.

The Genus Alnus, A Comprehensive Outline of Its Chemical Constituents and Biological Activities

The genus Alnus (Betulaceae) is comprised of more than 40 species. Many species of this genus have a long history of use in folk medicines. Phytochemical investigations have revealed the presence of diarylheptanoids, polyphenols, flavonoids, terpenoids, steroids and other compounds. Diarylheptanoids, natural products with a 1,7-diphenylheptane structural skeleton, are the dominant constituents in the genus, whose anticancer effect has been brought into focus. Pure compounds and crude extracts from the genus exhibit a wide spectrum of pharmacological activities both in vitro and in vivo. This paper compiles 273 naturally occurring compounds from the genus Alnus along with their structures and pharmacological activities, as reported in 138 references.

Phytochemical, antioxidant and hepatoprotective effects of Alnus nitida bark in carbon tetrachloride challenged Sprague Dawley rats

BACKGROUND

Alnus nitida (Spach) Endl. is traditionally used for inflammatory disorders. Diarylheptanoids constituents having diverse therapeutically importance including hepato-protective was reported in A. nitida. The aim of this study was to explore the antioxidant and hepato-protective profile of A. nitida stem bark's crude methanol extract (ANM).

METHODS

Crude methanol extract of A. nitida stem bark and its derived fractions were assessed for phytochemical classes and in vitro antioxidant profiling by multidimensional assays. Hepato-protective assessment of ANM was investigated on rats, which were made hepatotoxic using carbon tetrachloride (CCl4). Additionally HPLC-DAD analysis of ANM, and its derived ethyl acetate and aqueous fraction was carried out to determine the presence of active constituents.

RESULTS

Qualitative analysis of crude extract-and its fractions depicted the presence of terpenoids, saponins, coumarins, phenols and flavonoids. Maximum quantity of total phenolic content (TPC) and total flavonoid content (TFC) was recorded in ANM and its derived fractions; n-hexane (ANH), chloroform (ANC), ethyl acetate (ANE) and the residual aqueous (ANA). ANM exhibited the best total antioxidant capacity, total reducing power, and scavenging of DPPH and OH radicals. ANE and ANA exhibited strong scavenging potential for iron chelation, nitric oxide and β-carotene bleaching assay. ANM treatment converse the activities of serum-marker enzymes and lipid profile, altered by CCl4 treatment in rat. CCl4 induced hepatic-cirrhosis in rat resulted in decrease of antioxidant enzyme activities such as catalase, peroxidase, superoxide dismutase, glutathione peroxidase, glutathione-S-transferase and glutathione reductase-which were restored towards the normal level with ANM. Similarly diminished level of reduced glutathione while enhanced level of lipid peroxides, hydrogen peroxide and nitrite in liver of cirrhotic rats was normalized by treatment of ANM. The histopathological studies of liver tissues also represented that ANM possessed the hepato-protective activity. HPLC-DAD analysis against eight known standards confirmed the presence of gallic acid, catechin and rutin in ANM and in ANA while in ANE gallic acid was only detected.

CONCLUSION

Based on the results of antioxidants, restoration of various antioxidant enzymes and histopathological studies, the recent study concludes that antioxidant potential of A. nitida bark might protect the liver damages.

Structural differences in diarylheptanoids analogues from Alnus viridis and Alnus glutinosa influence their activity and selectivity towards cancer cells

Diarylheptanoids represent a group of plant secondary metabolites that possess multiple biological properties and are increasingly recognized for their therapeutic potential. A comparative study was performed on structurally analogous diarylheptanoids isolated from the bark of green (Alnus viridis) and black alder (Alnus glutinosa) to address their biological effects and determine structure-activity relationship. The structures and configurations of all compounds were elucidated by NMR, HR-ESI-MS, UV and IR. Diarylheptanoids actions were studied in human non-small cell lung carcinoma cells (NCI-H460) and normal keratinocytes (HaCaT). A. viridis compounds 3v, 5v, 8v and 9v that possess a carbonyl group at C-3 were considerably more potent than compounds without this group. A. viridis/A. glutinosa analogue pairs, 5v/5g and 9v/9g, which differ in the presence of 3' and 3″-OH groups, were evaluated for anticancer activity and selectivity. 5v and 9v that do not possess 3' and 3″-OH groups showed significantly higher cytotoxicity compared to analogues 5g and 9g. In addition, these two A. viridis compounds induced a more prominent apoptosis in both cell lines and an increase in subG0 cell cycle phase, compared to their A. glutinosa analogues. 5v and 9v treatment triggered intracellular superoxide anion accumulation and notably decreased mitochondrial transmembrane potential. In HaCaT cells, 9v and 9g with a 4,5 double bond caused a more prominent loss of mitochondrial transmembrane potential compared to 5v and 5g which possess a 5-methoxy group instead. Although green alder diarylheptanoids 5v and 9v displayed higher cytotoxicity, their analogues from black alder 5g and 9g could be more favorable for therapeutic use since they were more active in cancer cells than in normal keratinocytes. These results indicate that minor differences in the chemical structure can greatly influence the effect of diarylheptanoids on apoptosis and redox status and determine their selectivity towards cancer cells.

Diarylheptanoids from Alnus nepalensis attenuates LPS-induced inflammation in macrophages and endotoxic shock in mice

Diarylheptanoids, a group of plant secondary metabolites are increasingly recognized as potential therapeutic agents. The aim of study was to ascertain the anti-inflammatory profile of diarylheptanoids from Alnus nepalensis against lipopolysaccharide (LPS)-induced inflammation in macrophages and endotoxic shock in mice. Extracts prepared from dried leaves of A. nepalensis using standard solvents were tested against LPS-induced inflammation in macrophages. Among all, butanol extract (ANB) has shown most significant inhibition of pro-inflammatory cytokines without any cytotoxicity. HPLC analysis of ANB showed the presence of diarylheptanoids. The diarylheptanoids were further isolated and tested in-vitro for anti-inflammatory activity. Treatment of isolated diarylheptanoids (HOG, ORE and PLS) was able to reduce the production and mRNA level of pro-inflammatory cytokines (TNF-α and IL-6). Furthermore, we demonstrated that it inhibited the expression of NF-kB protein in LPS-induced inflammation in macrophages. In-vivo efficacy and safety profile of ANB revealed that oral treatment of ANB was able to improve the survival rate, and inhibited the production of pro-inflammatory cytokines in serum, attenuated vital organ injury in a dose dependent manner without any toxic effect at higher dose in mice. The results suggest that diarylheptanoids from A. nepalensis can be considered as potential therapeutic candidates for the management of inflammation related diseases.