Rocío Rodríguez-Arcos

The Flavonol Isorhamnetin Exhibits Cytotoxic Effects on Human Colon Cancer Cells

The aim of this study was to determine whether isorhamnetin, an immediate 3-O-methylated metabolite of quercetin, affects proliferation, cell death, and the cell cycle of human colon carcinoma (HCT-116) cells. Isorhamnetin was found to be a potent antiproliferative agent in a dose- and time-dependent manner, with an IC50 of 72 μM after 48 h of incubation as estimated by MTT assay. Flow cytometry and fluorescence microscopy analysis showed that isorhamnetin exerted a stimulatory effect on apoptosis and necrosis. Isorhamnetin also increased the number of cells in G2/M phase. Serum deprivation appeared to potentiate the effects of isorhamnetin on cell death and facilitated cell cycle progression to G0/G1 phase. These results suggest that isorhamnetin might mediate inhibition of HCT-116 cell growth through the perturbation of cell cycle progression and are consistent with the notion that G2/M checkpoints could be a conserved target for flavonoids in human colon cancer cells, leading to apoptotic and necrotic death. These antiproliferative, apoptotic, necrotic, and cell cycle effects suggest that isorhamnetin may have clinically significant therapeutic and chemopreventive capabilities. To our knowledge, this is the first report of the effect of isorhamnetin on human colon cancer cells.

Flavonoid Profile of Green Asparagus Genotypes

The determination of flavonoid profiles from different genotypes of triguero asparagus and their comparison to those from green asparagus commercial hybrids was the main goal of this study. The samples consisted of 32 commercial hybrids and 65 genotypes from the Huetor-Tajar population variety (triguero). The analysis of individual flavonoids by HPLC-DAD-MS has allowed the determination of eight naturally occurring flavonol derivatives in several genotypes of triguero asparagus. Those compounds included mono-, di-, and triglycosides of three flavonols, that is, quercetin, isorhamnetin, and kaempferol. The detailed analysis of the flavonoid profiles revealed significant differences among the distinct genotypes. These have been classified in three distinct groups as the result of a k-means clustering analysis, two of them containing both commercial hybrids and triguero asparagus and another cluster constituted by 21 genotypes of triguero asparagus, which contain several key flavonol derivatives able to differentiate them. Hence, the triglycosides tentatively identified as quercetin-3-rhamnosyl-rutinoside, isorhamnetin-3-rhamnosyl-rutinoside, and isorhamnetin-3-O-glucoside have been detected only in the genotypes grouped in the above-mentioned cluster. On the other hand, the compound tentatively identified as isorhamnetin-3-glucosyl-rutinoside was present in most genotypes of triguero asparagus, whereas it has not been detected in any of the commercial hybrids.

Dietary fiber from Tunisian common date cultivars (Phoenix dactylifera L.): chemical composition, functional properties, and antioxidant capacity.

The dietary fibers (DF) of 10 date varieties from Tunisian oases have been investigated. Further knowledge on the content, composition, and technological applications of those fibers could support their genetic variability and promote the socioeconomical development of growing areas. The composition, water- and oil-holding capacities, solubility, and antiradical activity have been determined. The DF content ranged from 4.7% (Matteta, Rochdi) to >7% (Deglé Nour, Garen Gaze, Smeti). Composition varied significantly among cultivars, and the results evidenced that uronic acids and lignin determine to a great extent the organoleptic quality of dates. Many of the varieties that have been studied (Garen Gaze, Matteta, Kenta, Rochdi, Mermella, Korkobbi, Eguwa) were selected because of great interest from technological and functional points of view. Among their physicochemical characteristics, these samples presented water- and oil-holding capacities of higher than 17 and 4 mL/g fiber, respectively, which make them suitable for use as additives in fiber-enriched foods. Also, DF of Garen Gaze, Smeti, Mermella, and Eguwa had a high antiradical capacity (>230 Trolox equiv/kg fiber). It was concluded that some of these varieties could be grown as potential sources of DF, which could be included in the formulation of fiber- and antioxidant-enriched foods.

3,4-Dihydroxyphenylglycol (DHPG): an important phenolic compound present in natural table olives.

The presence of 3,4-dihydroxyphenylglycol (DHPG) was studied in 32 samples and 10 different cultivars of natural table olives, using an accurate method to avoid wrong quantification. Hydroxytyrosol (HT), tyrosol, and verbascoside were also quantified, as these four compounds comprise the majority of the chromatographic profile. Analyses were carried out by HPLC-DAD-UV after extraction of all phenolics, and hydroxytyrosol was the major component in nearly all samples. High levels of DHPG (up to 368 mg/kg of dry weight) were found in the pulp of natural black olives independent of cultivar and processing method, similar to its concentration in the brine in almost all of the samples. The presented data for this antioxidant indicate that natural table olives are a rich source of DHPG and hydroxytyrosol, compounds with interesting nutritional and antioxidant properties.

Optimization of a method for the profiling and quantification of saponins in different green asparagus genotypes.

The main goal of this study was the optimization of a HPLC-MS method for the qualitative and quantitative analysis of asparagus saponins. The method includes extraction with aqueous ethanol, cleanup by solid phase extraction, separation by reverse phase chromatography, electrospray ionization, and detection in a single quadrupole mass analyzer. The method was used for the comparison of selected genotypes of Huétor-Tájar asparagus landrace and selected varieties of commercial diploid hybrids of green asparagus. The results showed that while protodioscin was almost the only saponin detected in the commercial hybrids, eight different saponins were detected in the Huétor-Tájar asparagus genotypes. The mass spectra indicated that HT saponins are derived from a furostan type steroidal genin having a single bond between carbons 5 and 6 of the B ring. The total concentration of saponins was found to be higher in triguero asparagus than in commercial hybrids.

Saponin Profile of Green Asparagus Genotypes

The main goal of this study was to determine the saponin profiles of different triguero asparagus genotypes and to compare them to green asparagus commercial hybrids. The samples consisted of 31 commercial hybrids and 58 genotypes from the Huétor-Tájar (HT) population variety (triguero). The saponin analysis by high-performance liquid chromatography-mass spectrometry allowed for the determination of 12 saponins derived from a furostan-type steroidal genin, 4 of which had never been described in the edible part of asparagus. The saponin profile of triguero asparagus was a combination of these new saponins and protodioscin. Although protodioscin was the major saponin found in commercial hybrids, some of these 12 saponins were detected as major components in some of the commercial hybrids. The total contents of saponins described in some of these HT genotypes reach values as high as 10-100 times higher than those found in commercial hybrids.

Asparagus byproducts as a new source of peroxidases

Soluble peroxidase (POD) from asparagus byproducts was purified by ion exchange chromatographies, and its kinetic and catalytic properties were studied. The isoelectric point of the purified isoperoxidases was 9.1, and the optimum pH and temperature values were 4.0 and 25 °C, respectively. The cationic asparagus POD (CAP) midpoint inactivation temperature was 57 °C, which favors its use in industrial processes. The Km values of cationic asparagus POD for H₂O₂ and ABTS were 0.318 and 0.634 mM, respectively. The purified CAP is economically obtained from raw materials using a simple protocol and possesses features that make it advantageous for the potential use of this enzyme in a large number of processes with demonstrated requirements of thermostable POD. The results indicate that CAP can be used as a potential candidate for removing phenolic contaminants.

Saponin Profile of Wild Asparagus Species

The aim of this work was to study the saponin profiles from spears of different wild asparagus species in the context of its genetic diversity aside from geographical seed origin. They included Asparagus pseudoscaber Grecescu, Asparagus maritimus (L.) Mill., Asparagus brachiphyllus Turcz., Asparagus prostrates Dumort., and Asparagus officinalis L. The saponin analysis by LC-MS has shown that saponin profile from wild asparagus is similar to that previously described for triguero asparagus from Huétor-Tájar landrace (triguero HT), which had not ever been reported in the edible part of asparagus. All the samples, except A. officinalis, were characterized for having saponins distinct to protodioscin and the total saponin contents were 10-fold higher than those described for commercial hybrids of green asparagus. In particular, A. maritimus from different origins were rich in saponins previously found in triguero HT. These findings supported previous suggestion, based on genetic analysis, about A. maritimus being the origin of triguero HT. Multivariate statistics including principal component analysis and hierarchical clustering analysis were used to define both similarities and differences among samples. The results showed that the greatest variance of the tested wild asparagus could be attributed to differences in the concentration of particular saponins and this knowledge could be a tool for identifying similar species.

The phytochemical and bioactivity profiles of wild Asparagus albus L. plant

The ethanolic extracts from the leaves, pericarps and rhizomes of Asparagus albus L. were investigated for their phytochemical composition, antioxidant (DPPH and FRAP assays), anti-microbial against human pathogenic isolates and cytotoxic (human colon carcinoma HCT-116 cells) activities. The highest flavonoid content was obtained in the leaf extract followed by the pericarp but there were no flavonoids detected in the rhizome. However, the rhizome had a high concentration of saponins. Flavonoid and saponin profiles were similar to those previously described for the triguero Huetor Tajar asparagus landrace. It was found that the pericarp ethanolic extract exhibited higher antioxidant activity than rhizome and leaf extracts. Moreover, the rhizome possessed more evident cytotoxic activity against HCT-116 cells in comparison to leaf and pericarp. All extracts showed varying degrees of antimicrobial activity against most of the human pathogenic isolates. In addition, the leaves showed more powerful inhibitory activities against the maximum number of bacteria and all the fungai isolated and the highest activity was in the pericarp extract against multidrug resistant Pseudomonas aeruginosa (MDR) and Erythromycin resistant Streptococcus agalactiae (ER) with an inhibition zone of 21mm and 19mm, respectively. The results show that A. albus could be a new crop with pharmaceutical interest because its richness in bioactive compounds provides considerable benefits for human health.

In Vitro Toxicity of Asparagus Saponins in Distinct Multidrug-Resistant Colon Cancer Cells

Colorectal cancer is the third most common cancer in the world. Many efforts have focused on finding natural molecules with potential chemo‐preventive activity due to their low toxicity compared to synthetic drugs. However, comprehensive information on the bioactive fractions and components is still missing. In this study, we developed a method for the quantitative separation and isolation of saponins from asparagus genotypes consisting of an adsorption chromatography and subsequent liquid chromatographic separation on a reversed‐phase column. The saponins isolated were tested for their cytotoxic activity against human colon cancer cell lines, which could develop cross‐resistance to a wide variety of chemotherapeutic drugs. Our results showed that Huétor‐Tájar asparagus saponins (HTSAP), mainly protodioscin and HTSAP‐10 have higher cytotoxic activity than HTSAP‐1, HTSAP‐6, and HTSAP‐8. This study links the potential anticancer effect of asparagus to specific saponins and unveils the triguero Huétor‐Tájar asparagus as a nutraceutical particularly in colon cancer therapies.