Effect of andrographolide and deep eutectic solvent extracts of Andrographis paniculata on human coronavirus organ culture 43 (HCoV-OC43)

BACKGROUND

Andrographis paniculata (Burm. f.) Nees has demonstrated potential for treating infections caused by coronaviruses. However, no antiviral activity of andrographolide or A. paniculata extracts against human coronavirus organ culture 43 (HCoV-OC43) has been reported.

PURPOSE

This study aimed to evaluate the anti-HCoV-OC43 effect of andrographolide and A. paniculata as well as the correlation between andrographolide concentration and the anti-HCoV-OC43 activity of A. paniculata extracts.

METHODS

This study evaluated and compared the in vitro anti-HCoV-OC43 activities of various A. paniculata extracts and andrographolide. To obtain A. paniculata extracts with different concentrations of andrographolide and its components, methanol and deep eutectic solvents (DES) were used to extract the aerial parts of A. paniculata. Andrographolide content was determined using UV-HPLC, and antiviral activity was assessed in HCT-8 colon cells.

RESULTS

The methanol and five acidic DES (containing malic acid or citric acid) extracts of A. paniculata exerted anti-HCoV-OC43 activity. Antiviral activity had a moderately strong positive linear relationship (r = 0.7938) with andrographolide content. Although the methanol extract contained the highest andrographolide content (2.34 mg/ml), its anti-HCoV-OC43 activity was lower than that of the DES extracts containing lower andrographolide concentrations (0.92-1.46 mg/ml).

CONCLUSION

Methanol and the five acidic DES extracts of A. paniculata exhibited anti-HCoV-OC43 activity. However, the in vitro antiviral activity of A. paniculata extracts did not have a very strong positive linear relationship (r < 0.8) with andrographolide concentration in the extract. As a result, when comparing A. paniculata extracts, the anti-HCoV-OC43 test could provide a different result from the andrographolide concentration determination.

Evaluating the in Vitro Efficacy of Quassinoids from Eurycoma longifolia and Eurycoma harmandiana against Common Cold Human Coronavirus OC43 and SARS-CoV-2 Using In-Cell Enzyme-Linked Immunosorbent Assay

Coronavirus disease-2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection, has become a pandemic and public health crisis. SARS-CoV-2 and the seasonal common cold coronavirus (HCoV-OC43) belong to the beta genus of human coronaviruses (HCoVs). In-cell ELISA assays were performed using HCoV-OC43 and SARS-CoV-2 and evaluated the antiviral activity of herbal plants. Eurycoma longifolia (EL) and Eurycoma harmandiana (EH) roots (antipyretic properties) and their constituent quassinoids, especially chaparrinone and eurycomalactone, showed potent anti-HCoV-OC43 and SARS-CoV-2 activities, and the low IC₅₀ values of the mentioned constituents were observed in the range of 0.32-0.51 μM. Eurycomanone and 13β,21-dihydroeurycomanone may contribute to the antiviral activity of EL, whereas chaparrinone is the major and active antiviral constituent of EH root. The content of quassinoids, β-carboline, and canthin-6-one alkaloids and the cytotoxicity profile of EL and EH extracts were varied regarding extraction solvents. The boiled water and 50% EtOH extractions of both plants were less toxic than those with 95% EtOH as the extraction solvent. Our research suggests that quassinoids, which come from EL and EH roots and are anti-coronavirus compounds, are potential treatment candidates for COVID-19 and merit further in vivo investigations.

Establishment of Afgekia mahidolae B.L. Burtt & Chermsir in vitro culture and effect of elicitation on its bioactive compounds

Afgekia mahidolae is a rare plant species that possesses antioxidant, antimicrobial, and wound healing properties. This study aimed to establish the in vitro culture of A. mahidolae and investigate the effects of elicitors on their phenolic and flavonoid production, including the antioxidant activities. The established callus was prepared in the form of cell suspension cultures to determine the effect of elicitors. After elicitation for 3 days, A. mahidolae cell suspension cultures treated by 5 µM salicylic acid or 100 mg/L yeast extract exhibited significantly higher levels of total phenolic and total flavonoid content than untreated cultures, which correlated to the antioxidant activities. In addition, the profiles of phenolic and flavonoid compounds in the callus and intact leaves of A. mahidolae were determined by LC-MS, which showed different phytochemicals. The findings of this study may encourage more sustainable development of A. mahidolae cultivation.

Effectiveness of neutral electrolyzed water in inactivating HCoV-OC43 and SARS-CoV-2 on the surfaces of plastic and the medicinal plant Centella asiatica (L.) urban

Concerns have been raised about viral contamination, including in crops due to the recent coronavirus disease 2019 pandemic. Limited evidence is available to support the use of sanitizing agents for human coronavirus-contaminated medicinal plants. Thus, we aimed to investigate the persistence of infectious human coronavirus OC43 (HCoV-OC43) as a SARS-CoV-2 surrogate in storage conditions and the capability of neutral electrolyzed water (NEW) to inactivate coronavirus, including in fresh plants such as C. asiatica. The levels of infectious HCoV-OC43 and the triterpenoid content of C. asiatica were quantified using a plaque assay and high-performance liquid chromatography, respectively. The results showed that the persistence of HCoV-OC43 on C. asiatica leaves is identical to that on inert polystyrene. When covered and kept at room temperature with high humidity (>90% RH), HCoV-OC43 can be stable on C. asiatica leaves for at least 24 h. NEW with 197 ppm of available chlorine concentration (ACC) was effective in inactivating both infectious HCoV-OC43 and SARS-CoV-2 in suspension (≥3.68 and ≥4.34 log reduction, respectively), and inactivated dried HCoV-OC43 on the surfaces of C. asiatica leaves (≥2.31 log reduction). Soaking C. asiatica leaves for 5 min in NEW with 205 ppm of ACC or water resulted in significantly higher asiaticoside levels (37.82 ± 0.29 and 35.32 ± 0.74 mg/g dry weight, respectively), compared to the unsoaked group (29.96 ± 0.78 mg/g dry weight). These findings suggest that although coronavirus-contaminated C. asiatica leaves can pose a risk of transmission, NEW could be an option for inactivation.

A modified IgG avidity assay for reliability improvement of an in-house capture ELISA to discriminate primary from secondary dengue virus infections

Although discrimination between primary and secondary dengue infections can be performed using commercially available immunoassays or in-house tests, the evaluation of these methods is important, but is often problematic due to incomplete clinical data. In many cases, patients' sera submitted to the laboratory may not include the date of onset of illness which is necessary to discriminate primary and secondary dengue infections. This study reports improvement of an in-house capture ELISA using IgG avidity to discriminate primary and secondary dengue virus infection. Modified definition criteria were applied to characterize 99 single sera based on their IgM/IgG ratios. Regressive analysis indicated that the avidity test results (avidity index of 60 % as cutoff) for the discrimination showed good agreement (96 %) and a high correlation (r = -0.81) with those of the in-house capture ELISA (IgM/IgG ratio at 1.2 as cutoff). To further evaluate the in-house tests, 318 convalescent sera were compared with a Focus Diagnostics' anti-dengue IgM ELISA. Compared with the Focus Diagnostics system, the sensitivity of an in-house IgM determination was 83 %, whereas using both IgM and IgG capture ELISAs the sensitivity increased to 95 %.

Improvement of stilbenoid production by 2-hydroxypropyl-β-cyclodextrin in white mulberry (Morus alba L.) callus cultures

Mulberroside A, oxyresveratrol and resveratrol, commonly found in Morus alba L., are potent anti-aging phytostilbenes. In this study, the effect of the addition of 2-hydroxypropyl-β-cyclodextrin on the levels of phytostilbenes in M. alba callus cultures was investigated. Commercial cyclodextrin was used in the hydrolytic and culture processes of the M. alba callus cultures. The hydrolytic study indicated that 2-hydroxypropyl-β-cyclodextrin acted as a retardant for stilbenoid hydrolysis. It reduced mulberroside A deglycosylation and stabilised oxyresveratrol. The elicitation result showed that extracellular oxyresveratrol was increased by adding 2-hydroxypropyl-β-cyclodextrin to the culture media of both free and immobilised M. alba callus (>730-fold and >169-fold, respectively) compared with those of the control. However, the intracellular mulberroside A levels in the treatment groups did not increase compared with those of the control. The results show that the addition of 2-hydroxypropyl-β-cyclodextrin significantly changed the patterns and levels of the stilbenoids in M. alba callus cultures.

Alginate immobilization of Morus alba L. cell suspension cultures improved the accumulation and secretion of stilbenoids

Morus alba L. (Moraceae) has been used in traditional medicine for the treatment of several illnesses. Recent research also revealed several pharmacological activities from many groups of secondary metabolites, including the stilbenoids mulberroside A, oxyresveratrol, and resveratrol, which are promising compounds for cosmetic and herbal supplement products. In our previous study, cell cultures of M. alba showed high productivity of these compounds. In this study, we attempted to develop immobilized cell cultures of M. alba and to test the effect of elicitors and precursors on the production of stilbenoids. The immobilization of the M. alba cells significantly promoted the secretion of mulberroside A into the extracellular matrix and culture media to 60%, while enhancing the level of oxyresveratrol and resveratrol by 12- and 27-fold, respectively. The elicitation of immobilized cells with a combination of 50 µM methyl jasmonate and 0.5 mg/mL yeast extract for 24 h promoted a twofold increase in the production of all three stilbenoids. Furthermore, the addition of 0.05 mM L-phenylalanine, 0.03 mM L-tyrosine, or a combination resulted in the enhancement of mulberroside A production for up to twofold. The addition of L-tyrosine significantly enhanced the production of oxyresveratrol and resveratrol. This is the first report of stilbenoid production using immobilized cell cultures of M. alba. The cultures have benefits over normal cell suspension cultures by promoting the secretion of mulberroside A and enhancing the levels of oxyresveratrol and resveratrol. Thus, it could be a candidate method for the production of these stilbenoids.

A pilot pharmacokinetic study of miroestrol and deoxymiroestrol on rabbit sera using polyclonal antibody-based icELISA analysis

Miroestrol (ME) and deoxymiroestrol (DME) are the most potent phytoestrogens and bioactive markers in Pueraria candollei var. mirifica tuberous roots. To understand their pharmacokinetic profiles, a pharmacokinetic study of ME and DME, at 0.43 and 0.21 mg per kg body weight, respectively, in three rabbits was performed after orally administering a single dose of P. candollei var. mirifica enriched fraction extract. Two established polyclonal antibody-based indirect competitive enzyme-linked immunosorbent assays were validated to determine ME and DME in rabbit sera. In rabbits, the area under the 0- to 48-hr concentration-time curve of ME and DME were 854.92 and 1,692.84 ng·h/ml, respectively. The maximum concentration of ME was measured 1 hr after administration as 69.62 ± 8.28 ng/ml, and the maximum concentration of DME was measured at 3 hr as 81.8 ± 5.43 ng/ml. These results provide an initial approach for designing and studying the relationship between the ME and DME levels and their therapeutic effects based on their pharmacokinetic profiles.

Development of an Enzyme-Linked Immunosorbent Assay for Determination Of Miroestrol Using an Anti-miroestrol Monoclonal Antibody

Miroestrol is a chromene with potent estrogenic activity present in Pueraria candollei, commonly known as White Kwao Krua. Although this compound is only present in low amounts in the plant, it plays an important role in the estrogenic action of P. candollei products. As a tool for further studies about the efficacy and safety of P. candollei as a phytoestrogenic supplement, we generated a novel monoclonal antibody against miroestrol. This anti-miroestrol monoclonal antibody was used to develop an immunoassay for the determination of miroestrol content, which can be used for quality control purposes of P. candollei. The developed ELISA against miroestrol has a calibration range of 10-780 ng/mL miroestrol, a limit of detection of 3.5 ng/mL, and a limit of quantitation of 12.2 ng/mL. According to the validation analysis, the established ELISA is precise, accurate, specific, and sensitive for miroestrol detection in plants. Furthermore, the anti-miroestrol monoclonal antibody was used to prepare an immunoaffinity column for the isolation of miroestrol from the tuberous root of P. candollei. The column provides a simple procedure for miroestrol isolation, with a capacity of 3.91 µg of miroestrol per 1 mL of immunogel.

Development of a Rapid Immunochromatographic Strip Test for the Detection of Mulberroside A

INTRODUCTION

Mulberroside A (MuA) is the major active anti-tyrosinase compound in the root bark extract of Morus alba L. (Moraceae). Typically, MuA is widely employed as an active ingredient in whitening cosmetics. A rapid and simple assay system utilizing a small quantity of test sample is essential for the detection of MuA in large number of samples. An immunoassay using highly specific MuA polyclonal antibodies may be useful for the determination of small quantities of MuA in test samples.

OBJECTIVE

To establish a rapid qualitative MuA test, an immunochromatographic strip test was developed using anti-MuA polyclonal antibodies (anti-MuA PAb).

METHODOLOGY

The qualitative assay was based on a competitive immunoassay where the detection reagent consisted of anti-MuA PAb colored with colloidal gold particles. The capture reagent was a MuA-ovalbumin (MuA-OVA) conjugate immobilized on the test strip membrane.

RESULTS

A sample containing MuA and the detection reagent were incubated together with immobilized capture reagent on a nitrocellulose membrane. When MuA was present, it competed with the immobilized conjugates on the strip membrane to bind a limited amount of colored antibodies; thus, a positive sample showed no color on the capture spot zone. The detection limit for the strip test was 2 µg/mL. The developed immunochromatographic strip test was utilized to determine MuA in plants, medical preparations and cosmetic samples.

CONCLUSION

This immunochromatographic strip test is advantageous as a rapid, simple and sensitive screening method for the detection of MuA in plant extracts, cosmetic samples and pharmaceutical products.

Enhanced Mulberroside A Production from Cell Suspension and Root Cultures of Morus alba Using Elicitation

Morus alba L. has been used in Asian traditional medicine as an anti-inflammatory, anti-asthmatic, anthelmintic and as a whitening agent in cosmetic products. Mulberroside A is the major active compound from M. alba root bark. In this study, cell suspension and root cultures of M. alba were established, and the effect of the elicitors on the enhancement of mulberroside A production in M. alba was investigated. The cell suspension and root cultures of M. alba were exposed to elicitors and then mulberroside A contents were determined by an indirect competitive ELISA method. High levels of mulberroside A were obtained by addition of 100 and 200 μM salicylic acid with 24 h exposure time in cell suspension cultures (37.9 ± 1.5 and 34.0 ± 4.7 mg/g dry wt., respectively). Furthermore, addition of yeast extract at 2 mg/mL with 24 h exposure time can significantly increase mulberroside A contents from both cell suspension (3.2-fold) and root cultures (6.6-fold). Mulberroside A contents from both cell suspension and root cultures after treatment with elicitors are similar or higher than those found in the intact root and root bark of several years old M. alba. These results indicate that mulberry tissue cultures using the elicitation method are interesting alternative sources for mulberroside A production.

Enhanced Mulberroside A Production from Cell Suspension and Root Cultures of Morus alba Using Elicitation

Morus alba L. has been used in Asian traditional medicine as an anti-inflammatory, anti-asthmatic, anthelmintic and as a whitening agent in cosmetic products. Mulberroside A is the major active compound from M. alba root bark. In this study, cell suspension and root cultures of M. alba were established, and the effect of the elicitors on the enhancement of mulberroside A production in M. alba was investigated. The cell suspension and root cultures of M. alba were exposed to elicitors and then mulberroside A contents were determined by an indirect competitive ELISA method. High levels of mulberroside A were obtained by addition of 100 and 200 μM salicylic acid with 24 h exposure time in cell suspension cultures (37.9 ± 1.5 and 34.0 ± 4.7 mg/g dry wt., respectively). Furthermore, addition of yeast extract at 2 mg/mL with 24 h exposure time can significantly increase mulberroside A contents from both cell suspension (3.2-fold) and root cultures (6.6-fold). Mulberroside A contents from both cell suspension and root cultures after treatment with elicitors are similar or higher than those found in the intact root and root bark of several years old M. alba. These results indicate that mulberry tissue cultures using the elicitation method are interesting alternative sources for mulberroside A production.

Dicentrine Production in Callus and Cell Suspension Cultures of Stephania Venosa

The highest dicentrine content (19.5 ± 0.3 mg/g dry weight) from callus culture of Stephania venosa was achieved from stem segments cultured on MS medium supplemented with TDZ 0.5 mg/L and NAA 1.0 mg/L. Cell suspension cultures were established from callus cultured on MS liquid medium with the same plant growth regulators. Dicentrine production from S. venosa cell suspension cultures was obtained in the range of 15–26 mg/g dry weight. Elicitation in cell suspension cultures by chitosan (50 mg/L) and salicylic acid (2 mg/L) for 6 days significantly increased dicentrine content. Our findings indicate that callus and cell suspension cultures of S. venosa can produce high levels of dicentrine as an alternative source of plant materials.

Dicentrine production in callus and cell suspension cultures of Stephania venosa

The highest dicentrine content (19.5 +/- 0.3 mg/g dry weight) from callus culture of Stephania venosa was achieved from stem segments cultured on MS medium supplemented with TDZ 0.5 mg/L and NAA 1.0 mg/L. Cell suspension cultures were established from callus cultured on MS liquid medium with the same plant growth regulators. Dicentrine production from S. venosa cell suspension cultures was obtained in the range of 15-26 mg/g dry weight. Elicitation in cell suspension cultures by chitosan (50 mg/L) and salicylic acid (2 mg/L) for 6 days significantly increased dicentrine content. Our findings indicate that callus and cell suspension cultures of S. venosa can produce high levels of dicentrine as an alternative source of plant materials.