Improved Surface Display of Human Hyal1 and Identification of Testosterone Propionate and Chicoric Acid as New Inhibitors

Degradation of high molecular weight hyaluronic acid (HA) in humans is mainly catalyzed by hyaluronidase Hyal1. This enzyme is involved in many pathophysiological processes and therefore appears an interesting target for drug discovery. Until now, only a few inhibitors of human Hyal1 are known due to obstacles in obtaining active enzymes for inhibitor screening. The aim of the present work was to provide a convenient enzyme activity assay and show its feasibility by the identification of new inhibitors. By autodisplay, Escherichia coli F470 can present active Hyal1 on its surface. In this study, the inducible expression of Hyal1 on the cell surface of E. coli under the control of a rhamnose-dependent promoter (Prha) was performed and optimized. Enzyme activity per single cell was increased by a factor of 100 compared to the constitutive Hyal1 surface display, as described before. An activity of 6.8 × 10-4 mU per single cell was obtained under optimal reaction conditions. By this modified activity assay, two new inhibitors of human Hyal1 were identified. Chicoric acid, a natural compound belonging to the phenylpropanoids, showed an IC50 value of 171 µM. The steroid derivative testosterone propionate showed and IC50 value of 124 ± 1.1 µM. Both values were in the same order of magnitude as the IC50 value of glycyrrhizic acid (177 µM), one of the best known inhibitors of human Hyal1 known so far. In conclusion, we established a new enzyme activity assay for human Hyal1 and identified new inhibitors with this new assay method.

Hyal-1 inhibitors from the leaves of Phyllanthus muellerianus (Kuntze) Excell

ETHNOPHARMACOLOGICAL RELEVANCE

Leaves and twigs from Phyllanthus muellerianus Kuntze Excell are known to exert anti-inflammatory and antipyretic properties as well as wound healing properties. During a wide screening for human hyaluronidase-1 inhibitors from natural sources leaf extracts from P. muellerianus turned out to show basic anti-hyaluronidase activity. A detailed investigation of this effect should rationalize the potential anti-inflammatory activity of the extract for improved wound healing.

AIM OF THE STUDY

The following study aimed to characterize the anti-Hyal-1 activity of the extract from P. muellerianus and to pinpoint the responsible natural products responsible for this bioactivity.

MATERIALS AND METHODS

Using cell surface displayed human Hyal-1 on Escherichia coli, the activity of inhibitors was determined by the stains-all assay method. A hydroalcoholic extract PWE from P. muellerianus was subjected to bioactivity-guided fractionation. Active compounds were characterized by means of mass spectrometry and NMR.

RESULTS

PWE exerts a concentration dependent inhibition of Hyal-1 with an IC₅₀ of 80 μg/mL. Bioassay-guided fractionation revealed 13 compounds from the two most active fractions, mainly ellagitannins and flavonoid glycosides. The most activeHyal-1 inhibitor was found to be the ellagitannin chebulanin 10 (IC₅₀ 132 μM). This represents the first description of chebulanin in P. muellerianus.

CONCLUSIONS

The hydroalcoholic extract of P. muellerianus, as well as several subfractions obtained during bioassay-guided fractionation showed strong activity against Hyal-1. The main activity can be correlated to the ellagitanin chebulanin. Additionally, also synergistic effects are observed, indicating that the traditional use of aqueous extracts of P. muellerianus is justified, rather than the use of the isolated tannins. The traditional use of the plant as an anti-inflammatory agent for improved wound-healing can be rationalized by the anti-Hyal-1 activities of its constituents.

Isoflavonoids with inhibiting effects on human hyaluronidase-1 and norneolignan clitorienolactone B from Ononis spinosa L. root extract

Human hyaluronidase-1 (Hyal-1) is one of the main enzymes in the homeostasis of hyaluronic acid (HA), the main polysaccharide of extracellular matrix. Development of specific Hyal-1 inhibitors might be a promising target for improved wound healing, tissue regeneration, and looking at renal function for diuresis. By using surface-displayed Hyal-1 on Escherichia coli F470 cells, HA as substrate and stains-all method for quantification of undegraded HA, the respective enzyme activity can be determined easily. Based on the traditional use of extracts from the roots from Ononis spinosa L. (Restharrow root) as a weak diuretic to achieve flushing of the urinary tract and as an adjuvant in minor urinary complaints the herbal material was selected for bioactivity guided fractionation for compounds with Hyal-1 inhibition activity. Hot water and hydroalcoholic extracts showed moderate inhibiting effects (IC₅₀ 1.36 resp. 0.73 mg/mL) while dichloromethane extract exerted an IC₅₀ of 190 μg/mL. Bioassay guided fractionation of the dichloromethane extract yielded four isoflavonoids with anti Hyal-1 activity: onogenin 1, sativanone 2, medicarpin 3 and calycosin-D 4 with inhibition rates of 25.4, 61.2, 22.4 and 23.0%, respectively at test concentration level of 250 μM. The norneolignan clitorienolactone B 5, the first time described for the genus Ononis, was inactive. The IC₅₀ of sativanone, the most active compound was determined with 1501 μM, which was better than that of the positive control glycyrrhizinic acid (177 μM). Thus, a possible explanation for diuretic properties of Ononis spinosa L. root extract may be postulated from the results so far obtained.

Phytochemical Characterization of Low Molecular Weight Constituents from Marshmallow Roots (Althaea officinalis) and Inhibiting Effects of the Aqueous Extract on Human Hyaluronidase-1

Extract RE was obtained from the roots of Althaea officinalis in a yield of 8.1%, related to the dried plant material, by extraction with MeOH-H₂O (1:1), followed by precipitation with EtOH to remove high molecular weight constituents. Phytochemical investigation of RE revealed the presence of N-phenylpropenoyl-l-amino acid amides 1-5, 8% glycine betaine 6, about 9% total amino acids with proline as the main compound, and about 61% mono- and oligomeric carbohydrates with sucrose as the main compound. Further fractionation revealed the presence of a hypolaetin diglycoside (12) and four hypolaetin glycosides (7-9 and 11) with O-sulfocarbohydrate moieties; additionally, 4'-O-methylisoscutellarein-8-O-β-d-(3″-O-sulfo)glucuronopyranoside (10) and the diglycosylated coumarin haploperoside D (13) were identified. The hypolaetin-O-sulfoglycosides 7-10 are new natural products. RE inhibited the enzymatic activity of surface-displayed human hyaluronidase-1 on Escherichia coli F470 cells with an IC₅₀ of 7.7 mg/mL. RE downregulated mRNA expression of hyal-1 in HaCaT keratinocytes at 125 and 250 μg/mL, respectively. These data contribute to a deeper phytochemical understanding of marshmallow root extracts and to the positive influence of extracts used for therapy of irritated and inflamed buccal tissue and cough.