Purification and Characterization of the Principal Antimutagenic Bioactive as Ethoxy-Substituted Phylloquinone from Spinach (Spinacea oleracea L.) Based on Evaluation in Models Including Human Lymphoblast TK+/- Cells

Anti-proliferative effect and underlying mechanism of ethoxy-substituted phylloquinone (vitamin K1 derivative) from Spinacia oleracea leaf and enhancement of its extractability using radiation technology

In our previous studies, a novel antimutagenic compound, 2-ethoxy-3-(3,7,11,15-tetramethylhexadec-2-ethyl) naphthaquinone-1,4-dione (ethoxy-substituted phylloquinone; ESP) from spinach was characterized and mechanism contributing to its antimutagenicity was deduced. In the current study, anti-proliferative activity of ESP was assessed in lung cancer (A549) cells using MTT [3-(4,5-dimethylthiazole-2yl)-2,5-diphenyl tetrazolium bromide], clonogenic assays and cell cycle analysis. ESP treatment showed selective cytotoxicity against lung cancer cells and no cytotoxicity in normal lung (WI38) cells. Cell cycle analysis revealed that ESP treatment arrests A549 cell population in G2-M phase. In-silico analysis indicated positive drug-likeness features of ESP. Molecular docking showed H-bonding and hydrophobic interactions between ESP and B-DNA dodecamer residues at minor groove. SWATH-MS (Sequential Window Acquisition of All Theoretical Mass Spectra) based proteomic analysis indicated down-regulation of proteins involved in EGFR signaling, NEDDylation and other metabolic pathways and up-regulation of tumor suppressor (STAT1 and NDRG1) proteins. Treatment of spinach powder with gamma radiation (5-20 kGy) from cobalt (Co-60) enhanced the extractability of ESP up to 4.4-fold at the highest dose of 20 kGy. Scanning electron microscopy of spinach powder displayed decrease in smoothness and compactness with increase in radiation dose attributing to its enhanced extractability. Increase in the extractability of ESP with increasing radiation doses as measured by fluorescence intensity and dry weight basis was strongly correlated. Nonetheless, radiation treatment did not affect the functionality of ESP in terms of anti-proliferative and antimutagenic activities. Current findings thus highlight broad spectrum bioactivity of ESP from spinach, its underlying mechanism and applicability of radiation technology in enhancing extractability.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13205-022-03264-6.

Secondary product from strawberry (Fragaria ananassa) fruit for extended preservation and value addition

Strawberry is highly delicate and perishable fruit prone to microbial spoilage. To address these issues, secondary product(s) using strawberry pulp was prepared by adding sweetener (jaggery or sucrose) and anti-browning agent (citrate) to reduce the extent of drying induced sourness and discoloration, respectively. Subsequently, these products were LDPE packed and radiation processed (≤ 5 kGy) to ensure microbiological safety during ambient temperature storage. Physical, biochemical, functional (antioxidant and antimutagenic) and organoleptic properties (including flavor compounds) were found to be either retained or enhanced compared to dehydrated strawberry pulp. The product termed as dehydrated strawberry roll having jaggery and citrate (DSRJ) was found to be more acceptable than that having sucrose and citrate (DSRS) till 5 months. Scanning electron microscopy indicated better surface quality of DSRJ than DSRS. Electrochemical property when analyzed using cyclic voltammetry displayed strong correlation to radical scavenging antioxidant assays with marginal storage associated shift in the peak potential. GC-MS analysis indicated retention of most of the flavor compounds in DSRJ during storage. Thus, DSRJ, a value-added product could provide a solution to control post-harvest losses of the fruit by processing to a more stable form and ensuring availability beyond the season.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s13197-021-05171-9.

Molecular mechanism of antimutagenicity by an ethoxy-substituted phylloquinone (vitamin K1 derivative) from spinach (Spinacea oleracea L.)

In our previous study, an antimutagenic compound from spinach (Spinacea oleracea L.), ethoxy-substituted phylloquinone (ESP) was isolated and characterized. The current study deals with elucidation of the possible mechanism of antimutagenicity of ESP against ethyl methanesulfonate (EMS) deploying model systems such as human lymphoblast (TK^+/- or TK6) cell line (thymidine kinase gene mutation assay) and Escherichia coli MG1655 (rifampicin resistance assay). Findings of the study ruled out the possibility of direct inactivation of EMS by ESP. DAPI competitive binding assay indicated the DNA minor groove binding activity of ESP. Interestingly, ESP did not display major groove binding or intercalating abilities. Further, proteomics study using 2-D gel electrophoresis in E. coli and subsequent studies involving single gene knockout strains revealed the possible role of tnaA (tryptophanase) and dgcP (diguanylate cyclase) genes in observed antimutagenicity. These genes have been reported to be involved in indole and cyclic-di-GMP biosynthesis, respectively, which eventually lead to cell division inhibition. In case of TK^+/- cell line system, ADCY genes (adenylate cyclase), a functional analogue of dgcP gene, were found to be transcriptionally up-regulated. The generation/doubling time were significantly higher in E. coli or TK^+/- cells treated with ESP than control cells. The findings indicated inhibition of cell proliferation by ESP through gene regulation as a possible mechanism of antimutagenicity across the biological system. Cell division inhibition actually provides additional time for the repair of damaged DNA leading to antimutagenicity.

Natural Predominance of Abscisic Acid in Pongammia pinnata ("Karanj") Honey Contributed to its Strong Antimutagenicity

Various samples of raw (unprocessed) floral honey collected from different geographical locations of India were assayed for its antimutagenicity against ethyl methanesulfonate in E. coli MG1655 cells through rifampicin resistance assay. A monofloral honey ("Pongammia pinnata", local name "Karanj") displayed maximum antimutagenicity (78.0 ± 1.7; P ≤ 0.05). Solid phase extraction (using Amberlite XAD-2 resin) followed by HPLC resulted into different peaks displaying varying antimutagenicity. Peak at retention time (R_t) 27.9 min (henceforth called P₂₈) displayed maximum antimutagenicity and was further characterized to be abscisic acid (ABA) using ESI-MS and NMR. Its antimutagenicity was reconfirmed through human lymphoblast cell line (TK6) mutation assay using thymidine kinase (tk^+/-) cell line. Although ABA from this honey displayed strong antimutagenicity, it lacked any in vitro antioxidant capacity indicating noninvolvement of any radical scavenging in the observed antimutagenicity.

Metal-free benzannulation of 1,7-diynes towards unexpected 1-aroyl-2-naphthaldehydes and their application in fused aza-heterocyclic synthesis

A novel I₂-mediated benzannulation of 1,7-diyne-involved 1,4-oxo-migration was established, providing unexpected 1-aroyl-2-naphthaldehydes. The resulting 1-aroyl-2-naphthaldehydes were successfully applied in the synthesis of polycyclic isoindoles.