Isothiocyanates and Glucosinolates from Sisymbrium officinale (L.) Scop. ("the Singers' Plant"): Isolation and in Vitro Assays on the Somatosensory and Pain Receptor TRPA1 Channel

Glucosinolates of Sisymbrium officinale and S. orientale

Glucosinolates (GSLs) from Sysimbrium officinale and S. orientale were analyzed qualitatively and quantitatively by their desulfo-counterparts using UHPLC-DAD-MS/MS. Eight GSLs were identified in S. officinale, including Val-derived (glucoputranjivin) and Trp-derived (4-hydroxyglucobrassicin, glucobrassicin, 4-methoxyglucobrassicin, and neoglucobrassicin) as the major ones followed by Leu-derived (Isobutyl GSL), Ile-derived (glucocochlearin) and Phe/Tyr-derived (glucosinalbin). Different S. orientale plant parts contained six GSLs, with Met-derived (progoitrin, epiprogoitrin, and gluconapin) and homoPhe-derived (gluconasturtiin) as the major ones, followed by glucosinalbin and neoglucobrassicin. GSL breakdown products obtained by hydrodistillation (HD) and microwave-assisted distillation from S. officinale, as well as isopropyl isothiocyanate, as the major volatile in both isolates, were tested for their cytotoxic activity using a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Generally, all volatile isolates showed similar activity toward the three cancer cell lines. The best activity was shown by isopropyl isothiocyanate at a concentration of 100 µg/mL after 72 h of incubation, with 53.18% for MDA-MB-231, 56.61% for A549, and 60.02% for the T24 cell line.

Potential Interplay between Nrf2, TRPA1, and TRPV1 in Nutrients for the Control of COVID-19

In this article, we propose that differences in COVID-19 morbidity may be associated with transient receptor potential ankyrin 1 (TRPA1) and/or transient receptor potential vanilloid 1 (TRPV1) activation as well as desensitization. TRPA1 and TRPV1 induce inflammation and play a key role in the physiology of almost all organs. They may augment sensory or vagal nerve discharges to evoke pain and several symptoms of COVID-19, including cough, nasal obstruction, vomiting, diarrhea, and, at least partly, sudden and severe loss of smell and taste. TRPA1 can be activated by reactive oxygen species and may therefore be up-regulated in COVID-19. TRPA1 and TRPV1 channels can be activated by pungent compounds including many nuclear factor (erythroid-derived 2) (Nrf2)-interacting foods leading to channel desensitization. Interactions between Nrf2-associated nutrients and TRPA1/TRPV1 may be partly responsible for the severity of some of the COVID-19 symptoms. The regulation by Nrf2 of TRPA1/TRPV1 is still unclear, but suggested from very limited clinical evidence. In COVID-19, it is proposed that rapid desensitization of TRAP1/TRPV1 by some ingredients in foods could reduce symptom severity and provide new therapeutic strategies.

Sisymbrium Officinale (the Singers' Plant) as an Ingredient: Analysis of Somatosensory Active Volatile Isothiocyanates in Model Food and Drinks

Sisymbrium officinale (L.) Scop. (hedge mustard) is a wild common plant of the Brassicaceae family. It is known as “the singers’ plant” for its traditional use in treating aphonia and vocal disability. The plant is rich in glucosinolates and isothiocyanates; the latter has been demonstrated to be a strong agonist in vitro of the Transient Receptor Potential Ankirine 1 (TRPA1) channel, which is involved in the somatosensory perception of pungency as well as in the nociception pathway of inflammatory pain. Volatile ITCs are released by the enzymatic or chemical hydrolysis of GLSs (glucosinolates) during sample crushing and/or by the mastication of fresh plant tissues when the plant is used as an ingredient. Some functional food and drink model preparations have been realised: honey enriched with seeds and flowers, infusions, cold drink (voice drink), artisanal beer, and a fermented tea (kombucha). Using SPME-GCMS chromatography, we analysed samples of the plant and of the food preparations adopting conditions that simulate the release of isothiocyanates (ITCs) during oral assumption. Two active compounds, iso-propylisothiocyanate and 2-butylisothiocyanate, have been assayed. The concentration of ITCs varies according to temperature, pH, grinding conditions, and different plant organs used. Kombucha-type fermentation seems to eliminate the ITCs, whereas they are retained in beer. The ITCs’ concentration is higher when entire seeds and flowers are used.

N-palmitoyl-D-glucosamine, a Natural Monosaccharide-Based Glycolipid, Inhibits TLR4 and Prevents LPS-Induced Inflammation and Neuropathic Pain in Mice

Toll-like receptors (TLRs) are key receptors through which infectious and non-infectious challenges act with consequent activation of the inflammatory cascade that plays a critical function in various acute and chronic diseases, behaving as amplification and chronicization factors of the inflammatory response. Previous studies have shown that synthetic analogues of lipid A based on glucosamine with few chains of unsaturated and saturated fatty acids, bind MD-2 and inhibit TLR4 receptors. These synthetic compounds showed antagonistic activity against TLR4 activation in vitro by LPS, but little or no activity in vivo. This study aimed to show the potential use of N-palmitoyl-D-glucosamine (PGA), a bacterial molecule with structural similarity to the lipid A component of LPS, which could be useful for preventing LPS-induced tissue damage or even peripheral neuropathies. Molecular docking and molecular dynamics simulations showed that PGA stably binds MD-2 with a MD-2/(PGA)3 stoichiometry. Treatment with PGA resulted in the following effects: (i) it prevented the NF-kB activation in LPS stimulated RAW264.7 cells; (ii) it decreased LPS-induced keratitis and corneal pro-inflammatory cytokines, whilst increasing anti-inflammatory cytokines; (iii) it normalized LPS-induced miR-20a-5p and miR-106a-5p upregulation and increased miR-27a-3p levels in the inflamed corneas; (iv) it decreased allodynia in peripheral neuropathy induced by oxaliplatin or formalin, but not following spared nerve injury of the sciatic nerve (SNI); (v) it prevented the formalin- or oxaliplatin-induced myelino-axonal degeneration of sciatic nerve. SIGNIFICANCE STATEMENT We report that PGA acts as a TLR4 antagonist and this may be the basis of its potent anti-inflammatory activity. Being unique because of its potency and stability, as compared to other similar congeners, PGA can represent a tool for the optimization of new TLR4 modulating drugs directed against the cytokine storm and the chronization of inflammation.

Moringin, A Stable Isothiocyanate from Moringa oleifera, Activates the Somatosensory and Pain Receptor TRPA1 Channel In Vitro

Moringa oleifera Lam. is a tropical plant widely used in traditional medicines and as a food supplement. It is characterized by the presence of glucosinolates and isothiocyanates; the stable isothiocyanate 4-[(α-l-rhamnosyloxy)benzyl]isothiocyanate (moringin) has been widely studied for its bioactivity as hypoglycemic, antimicrobial, anticancer and in particular for its involvement in nociception and neurogenic pain. Moringa extracts and pure moringin were submitted to in vitro assays with the somatosensory TRPA1 ion channel, proving that moringin is a potent and effective agonist of this receptor involved in nociceptive function and pain states. Moringin do not activate or activates very weakly the vanilloids somatosensory channels TRPV1,2,3 and 4, and the melastatin cooling receptor TRPM8. The comparison of moringin’s activity with other known agonists of natural origin is also discussed.

Glucosinolates in Sisymbrium officinale (L.) Scop.: Comparative Analysis in Cultivated and Wild Plants and in Vitro Assays with T2Rs Bitter Taste Receptors

Sisymbrium officinale (L.) Scop., commonly known as "hedge mustard" or "the singer's plant" is a wild plant common in Eurasian regions. Its cultivation is mainly dedicated to herboristic applications and it has only recently been introduced into Italy. The active botanicals in S. officinale are glucosinolates, generally estimated by using UV or high-performance liquid chromatography (HPLC). Using both techniques, we measured the total glucosinolates from S. officinale in different parts of the plant as roots, leaves, seeds, and flowers. A comparison was made for cultivated and wild samples, and for samples obtained with different pre-treatment and fresh, frozen, and dried storage conditions. Cultivated and wild plants have a comparable amount of total glucosinolates, while drying procedures can reduce the final glucosinolates content. The content in glucoputranjivin, which is the chemical marker for glucosinolates in S. officinale, has been determined using HPLC and a pure reference standard. Glucoputranjivin and two isothiocyanates from S. officinale have been submitted to in vitro assays with the platform of bitter taste receptors of the T2Rs family. The results show that glucoputranjivin is a selective agonist of receptor T2R16.