Bangladesh Journal of Pharmacology Volume: 19; Number 1; Year 2024 Cite this article as: Shankar S, Srinivasan C, Sathiavelu M. Anti-diabetic activity of Calathea anulque. Bangla- desh J Pharmacol. 2024; 19: 39-41. Anti-diabetic activity of Calathea anulque Sir, Calathea anulque is commonly known as the rattlesnake plant and originates from the tropical rainforests of South America. The foliage of this plant tends to be lanceolate in shape and color, with a distinctive rattle- snake-like pattern and a striking crimson backside. Because of the color variations and leaf patterns, the genus Calathea is widely used as an ornamental plant (Efzueni Rozali et al., 2014). C. warscewiczii is used in traditional Panamanian medicinal uses to treat diseases such as painful wounds and inflammation (Gupta et al., 2005). One of the plant genera, C. panamensis, exhibits potential anti-diabetic activity using the glucose 6- phosphatase assay and significant anti-radical activity using the DPPH trapping technique (Rodríguez et al., 2008). This study aims to evaluate the anti-diabetic properties and in vitro antioxidant effect of C. anulque leaf extracts. The fresh and healthy plant leaves were obtained from the Thotta Kalai nursery garden, ECR, Chennai, Tamil Nadu, India. The collected leaves were washed under running tap water to remove dust particles and then rinsed with Milli-Q water. Subsequently, the leaves were left to air dry in the shade for a week without direct sunlight exposure. Using an electric blender, the dried leaves were ground into a fine powder. The extraction process involved the use of two different solvents, such as methanol and ethyl acetate. A sterile 250 mL Erlenmeyer flask was filled with 100 mL of each solvent, and 1 g of finely ground leaf powder was added. The flasks were parafilm-sealed and kept in a shaker for 48 hours at 120 rpm. The concentrates were extracted by filtering through Whatman filter paper No. 1 after 48 hours. The filtrates were evaporated using a rotary vacuum to obtain dried crude extracts. The alpha-amylase method was carried out to deter- mine the anti-diabetic activity of C. anulque. The crude extracts were dissolved in Milli-Q water to produce four different concentrations (25, 50, 75, and 100 µg/ mL). As a blank, distilled water was used. As a control, a mixture of 1 µL distilled water and 500 µL amylase solution was used. About 500 µL of plant extract and amylase solution were combined in a 0.02 M sodium phosphate buffer (pH 6.9, 0.006 M sodium chloride) and incubated at 25ºC for 10 min. After pre-incubation, 500 µL of 1% starch solution was added to each tube at 5 sec intervals in 0.02 M sodium phosphate buffer (pH 6.9 with 0.006 M sodium chloride). The reaction mixture was incubated for 10 min at 25ºC. 1 mL of DNSA color reagent was added to stop the reaction. These test tubes were heated in a boiling water bath for 5 min and cooled to room temperature. The reaction mixture was diluted with 10 mL of distilled water, and the absor- bance was read at 540 nm using a UV-Vis spectro- photometer (Shah et al., 2020). The reference standard was acarbose. The percentage of inhibition was calcu- lated using the following formula: Percentage of amylase inhibition = Control absorbance – Test absorbance / Control absorbance × 100 The stable 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging assay was carried out to determine the antioxidant activity of C. anulque crude extracts according to the protocol (Al-Hadhrami and Hossain, 2016). About 1 mL of plant crude extracts of varying concentrations (25, 50, 75, and 100 µg/mL) were com- bined with 2 mL of 0.1 mM DPPH solution. Gallic acid was used as a reference standard. As a control, a mix- ture of 1 mL of methanol and 2 mL of DPPH solution was used. The mixture was shaken well and incubated in the absence of light (dark conditions) for 45 min. The absorbance of the reaction was measured at 517 nm in a UV-Vis spectrophotometer against the blank (metha- nol). The formula below was used to calculate the percent inhibition. %Scavenging effect = Control absorbance - Test absorbance / Control absorbance × 100 In α-amylase assay, C. anulque extracts showed signifi- cant inhibitory activity. Although compared to metha- nolic extract, ethyl acetate extract showed more inhibi- tion, with 87.3% at 100 µg/mL, followed by 83.8% at 75 µg/mL concentration. The standard acarbose showing 89.5% anti-diabetic activity at 100 µg/mL concentration (Figure 1A). In comparison to the ethyl acetate extract, the C. anulque methanolic extract exhibits the highest radical scaven- ging effect of about 79.7% at 100 µg/mL, followed by 76.2% at 75 µg/mL. whereas the ethyl acetate extract of C. anulque exhibited a potential antioxidant activity of 50.4% at a 100 µg/mL concentration. Ascorbic acid was taken as a standard, showing 96.0% antioxidant activity A Journal of the Bangladesh Pharmacological Society (BDPS) Bangladesh J Pharmacol 2024; 19: 39-41 Journal homepage: www.banglajol.info; www.bdpsjournal.org Abstracted/indexed in Academic Search Complete, Agroforestry Abstracts, Asia Journals Online, Bangladesh Journals Online, Biological Abstracts, BIOSIS Previews, CAB Abstracts, Current Abstracts, Directory of Open Access Journals, EMBASE/Excerpta Medica, Global Health, Google Scholar, HINARI (WHO), International Pharmaceutical Abstracts, Open J-gate, Science Citation Index Expanded, SCOPUS and Social Sciences Citation Index ISSN: 1991-0088; DOI: 10.3329/bjp.v19i1.70296 Letter to the Editor This work is licensed under a Creative Commons Attribution 4.0 International License. You are free to copy, distribute and perform the work. You must attribute the work in the manner specified by the author or licensor at 100 µg/mL concentration (Figure 1B). C. anulque exhibits significant levels of antioxidant and anti-diabetic properties in its methanolic and ethyl acetate extracts. Table I shows the data of some plant extracts with anti- diabetic and antioxidant effects for comparison. One might think of critical role of antioxidants in the treat- ment of diabetes. Some plant extracts exhibit parallel trends in both anti-diabetic and antioxidant effects, exemplified by Calathea anulque, others, such as Abel- moschus esculentus, shows a divergence with a subs- tantial anti-diabetic effect but a relatively lower antioxi- dant effect. Limitation of this study was as follows: a) the anti- diabetic effect was assessed by α-amylase activity, b) in vivo laboratory animal model was not done, and c) the active component within the extracts were not identi- fied. Financial support: Vellore Institute of Technology (SG ID: SG20220100) Conflict of interest: The authors declare that they have no con- flict of interest Acknowledgment: The authors thank Vellore Institute of Tech- nology, Vellore for providing a VIT seed grant for carrying out this research Saranya Shankar, Chitrashalini Srinivasan and Mythili Sathiavelu School of Bioscience and Technology, Vellore Institute of Technology, Tamil Nadu, India. Corresponding author: email: smythili@vit.ac.in References Ahmed BT, Kumar SA. Antioxidant and antidiabetic proper- ties of Abelmoschus esculentus extract: An in vitro assay. Res J Biotechnol. 2016; 11: 34-41. Al-Hadhrami RMS, Hossain MA. Evaluation of antioxidant, antimicrobial, and cytotoxic activities of seed crude extracts of Ammi majus grown in Oman. Egypt J Basic Appl Sci. 2016; 3: 329-34. Chauhan S, Kaur A, Vyas M, Khatik GL. Comparison of anti- diabetic and antioxidant activity of wild and cultivated variety of Rauwolia serpentine. 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Gupta MP, Solís PN, Calderón AI, Guinneau-Sinclair F, Correa 40 Bangladesh J Pharmacol 2024; 19: 39-41 25 50 75 100 Concentration (µg/mL) % In h ib it io n 100 50 0 B 25 50 75 100 Concentration (µg/mL) % In h ib it io n 100 80 60 40 20 0 A Ethyl acetate extract Methanolic extract Standard Figure 1: α-Amylase activity [anti-diabetic effect, (A)] and 2,2-diphenyl-1-picrylhydrazyl assay [antioxidant effect, (B)] of different extracts of Calathea anulque Table I Relation between anti-diabetic and antioxidant effects of different plant extracts Names Anti-diabetic effect (%) Antioxidant effect (%) References Paederia foetida (5000 µg/mL) 46.2 63.8 Ghosh et al., 2023 Sorghum halepense (2000 µg/mL) 62.4 74.1 Shah et al., 2017 Elaeocarpus ganitrus (200 µg/ml) 53.3 78.9 Talukdar et al., 2017 Abelmoschus esculentus (250 µg/mL) 91.6 28.2 Ahmed and Kumar, 2016 Hygrophila auriculata (100 µg/mL) 78.9 53.2 Rastogi et al., 2014 (100 µg/mL) 87.3 79.7 Present study Rauwolia serpentine ( 0.5 µg/mL) 58.4 84.6 mailto:mohanrajupu62@gmail.com mailto:smythili@vit.ac.in M, Galdames C, Guerra C, Espinosa A, Alvenda GI, Robles G, Ocampo R. 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