<Insert Table 2: Antioxidant activity (Percent Inhibition) of essential oil in DPPH free radical scavenging activity>
The assay result is presented as percentage inhibition of free radical in table 2. The results reveal that the essential oil of black cardamom extracted by MAHD and HD methods show concentration-dependent antioxidant activity. The percentage inhibition goes from 54.43 to 74.44 and from 47.44 to 64.84 for MAHD and HD extracted essential oil respectively as we increase concentration from 10 to 25 µg/ml. the percentage inhibition for MAHD and HD extracted oil was significantly lower as compared to standard ascorbic acid (AA).
< Insert Figure 7 Plot of percentage of DPPH radical scavenging capacity against the concentration of essential oils By MAHD and HD methods >
The IC50 values which we get from the plot of percentage of DPPH radical scavenging capacity against the concentration of essential oils (Fig. 7) for MAHD and HD extracted essential oils are 7.5 µg/ml and 12.71 µg/ml respectively. The percentage inhibition and IC50 values of the essential oil extracted by MAHD and HD techniques show that MAHD extracted oil has better antioxidant activity than the HD extracted oil. Biological activities such as antibacterial and antioxidant activity possibly allied with total phenolic content. The strong antioxidant activity of MAHD extracted essential oil is related to its higher phenolic content i.e. 1, 8-cineol[24][33].
Conclusion
In this study, the composition and yield of essential oil of Amomum subulatum were varied with the extraction methods. Microwave assisted hydrodistillation requires the significantly shorter time of extraction than conventional hydrodistillation method. The energy requirement is lesser in case of MAHD than traditional methods. This study also highlights that MAHD method is advantageous to recover more oxygenated monoterpenes (1, 8-cineol, Terpinen-4-ol and α-terpineol). However, the hydrocarbon monoterpenes such as α-pinene and β-pinene have a lower percentage of MAHD extract. Antibacterial activity of essential oil obtained by MAHD method is greater than HD. against both the studied microorganisms viz. Staphylococcus aureus and E. coli. Radical scavenging activity (DPPH) of both essential oils was good but essential oil extracted by MAHD showing better results.
Conflict of Interest : The authors declare that they have no conflict of interest.References
1. Rout PK, Sahoo D, Jena KS, Rao YR (2003) Analysis of the Oil of Large Cardamom ( Amomum subulatum Roxb.,) Growing in Sikkim. J Essent Oil Res 15:265–266. https://doi.org/10.1080/10412905.2003.9712138
2. Gilani; SR, Shahid; I, Mehmud; MJS, Ahme R (2006) Antimicrobial activities and physico chemical properties Antimicrobial Activities and Physico-Chemical Properties of the Essential Oil from Amomum Subulatum. Int J Appl Chem 2:81–86
3. Rao YS, Kumar A, Chatterjee S, et al (1993) Large cardamom ( Amomum subulatum Roxb .) -a review. J Spices Aromat Crop 2 1–15
4. Agnihotri S, Wakode S (2010) Antimicrobial activity of essential oil and various extracts of fruits of greater cardamom. Indian J. Pharm. Sci. 72:657–659
5. Bhatt M, Juyal V, Singh A (2014) Amomum Subulatum Roxb : A Critical Review of Pharmacological and Phytochemical Data. Int J Pharm Phytopharm Res 3:362–364
6. Verma SK, Jain V, Singh DP (2012) Effect of Greater cardamom (Amomum subulatum Roxb.) on blood lipids, fibrinolysis and total antioxidant status in patients with ischemic heart disease. Asian Pacific J Trop Dis 2:739–743. https://doi.org/10.1016/S2222-1808(12)60255-2
7. Berka-Zougali B, Ferhat MA, Hassani A, et al (2012) Comparative study of essential oils extracted from Algerian myrtus communis L. leaves using microwaves and hydrodistillation. Int J Mol Sci 13:4673–4695. https://doi.org/10.3390/ijms13044673
8. Bag A, Chattopadhyay RR (2015) Evaluation of synergistic antibacterial and antioxidant efficacy of essential oils of spices and herbs in combination. PLoS One 10:1–17. https://doi.org/10.1371/journal.pone.0131321
9. Gurudutt KN, Naik JP, Srinivas P, Ravindranath B (1996) Volatile constituents of large cardamom (Amomum subulatum Roxb.). Flavour Fragr J 11:7–9. https://doi.org/10.1002/(SICI)1099-1026(199601)11:1<7::AID-FFJ542>3.0.CO;2-9
10. Naik JP, Rao LJM, Kumar TMM, Sampathu SR (2004) Chemical composition of the volatile oil from the pericarp (husk) of large cardamom (Amomum subulatum Roxb.). Flavour Fragr J 19:441–444. https://doi.org/10.1002/ffj.1336
11. Kaskoos RA, Mir SR, Kapoor R, Ali M (2008) Essential Oil Composition of the Fruits of Amomum subulatum Roxb. J Essent Oil Bear Plants 11:184–187. https://doi.org/10.1080/0972060X.2008.10643617
12. Bajpai VK, Sharma A, Kim SH, Baek K-H (2015) Chemical Composition, Antioxidant, Lipid Peroxidation Inhibition and Free Radical Scavenging Activities of Microwave Extracted Essential Oil from Allium sativum . J Essent Oil Bear Plants 18:300–313. https://doi.org/10.1080/0972060X.2013.764215
13. Mandal V, Mohan Y, Hemalatha S (2007) Microwave Assisted Extraction – An Innovative and Promising Extraction Tool for Medicinal Plant Research. Pharmacogn Rev 1:7–18
14. Cardoso-Ugarte GA, Juárez-Becerra GP, Sosa-Morales ME, López-Malo A (2013) Microwave-assisted extraction of essential oils from herbs. J Microw Power Electromagn Energy 47:63–72
15. Kormin F, Ahmed I, Yunus RM, Yusof ZAM (2010) The potential of modified microwave extraction system (mmes) to extract bioactive components from ferns. Int J Eng Technol 10:7–21
16. Li X-J, Wang W, Luo M, et al (2012) Solvent-free microwave extraction of essential oil from Dryopteris fragrans and evaluation of antioxidant activity. Food Chem 133:437–444. https://doi.org/10.1016/j.foodchem.2012.01.056
17. Chan C-H, Yusoff R, Ngoh G-C, Kung FW-L (2011) Microwave-assisted extractions of active ingredients from plants. J Chromatogr A 1218:6213–6225. https://doi.org/10.1016/j.chroma.2011.07.040
18. Li Y, Fabiano-Tixier AS, Vian MA, Chemat F (2013) Solvent-free microwave extraction of bioactive compounds provides a tool for green analytical chemistry. Trends Anal Chem 47:1–11. https://doi.org/10.1016/j.trac.2013.02.007
19. Golmakani M-T, Rezaei K (2008) Comparison of microwave-assisted hydrodistillation withthe traditional hydrodistillation method in the extractionof essential oils from Thymus vulgaris L. Food Chem 109:925–930. https://doi.org/10.1016/j.foodchem.2007.12.084
20. M. R, Nour AH, Sulaiman ZA, et al (2014) A Comparative Study of Lemongrass (Cymbopogon Citratus) Essential Oil Extracted by Microwave-Assisted Hydrodistillation (MAHD) and Conventional Hydrodistillation (HD) Method. Int J Chem Eng Appl 5:104–108. https://doi.org/10.7763/IJCEA.2014.V5.360
21. Chen X, Zhang Y, Zu Y, et al (2011) Composition and biological activities of the essential oil from Schisandra chinensis obtained by solvent-free microwave extraction. LWT - Food Sci Technol 44:2047–2052. https://doi.org/10.1016/j.lwt.2011.05.013
22. Bhalerao MS, Patwardhan A V., Bhosale MA, et al (2016) Epoxidised soybean oil–Cu/Cu 2 O bio-nanocomposite material: synthesis and characterization with antibacterial activity. RSC Adv 6:38906–38912. https://doi.org/10.1039/C6RA00588H
23. I.P.S Kapoor , B. Singh , G. Singh , V. Isidorov LS (2008) Chemistry, antifungal and antioxidant activities of cardamom (Amomum subulatum) essential oil and oleoresins. Int J Essent Oil Ther 2:29–40
24. Abdelhady MI, Aly HAH (2012) Antioxidant antimicrobial activities of callistemon comboynensis essential oil. Free Radicals Antioxidants 2:37–41. https://doi.org/10.5530/ax.2012.2.8
25. Shekhar TC, Anju G (2014) Antioxidant Activity by DPPH Radical Scavenging Method of Ageratum conyzoides Linn. Leaves. Am J Ethnomedicine 1:244–249
26. Bousbia N, Abert Vian M, Ferhat MA, et al (2009) Comparison of two isolation methods for essential oil from rosemary leaves: Hydrodistillation and microwave hydrodiffusion and gravity. Food Chem 114:355–362. https://doi.org/10.1016/j.foodchem.2008.09.106
27. Desai MA, Parikh J (2012) Microwave Assisted Extraction of Essential Oil From Cymbopogon Flexuosus (Steud.) Wats.: A Parametric and Comparative Study. Sep Sci Technol 47:1963–1970. https://doi.org/10.1080/01496395.2012.659785
28. Ferhat MA, Meklati BY, Smadja J, Chemat F (2006) An improved microwave Clevenger apparatus for distillation of essential oils from orange peel. J Chromatogr A 1112:121–126. https://doi.org/10.1016/j.chroma.2005.12.030
29. Lucchesi ME, Smadja J, Bradshaw S, et al (2007) Solvent free microwave extraction of Elletaria cardamomum L.: A multivariate study of a new technique for the extraction of essential oil. J Food Eng 79:1079–1086. https://doi.org/10.1016/j.jfoodeng.2006.03.029
30. Erkan N, Ayranci G, Ayranci E (2008) Antioxidant activities of rosemary (Rosmarinus Officinalis L.) extract, blackseed (Nigella sativa L.) essential oil, carnosic acid, rosmarinic acid and sesamol. Food Chem 110:76–82. https://doi.org/10.1016/j.foodchem.2008.01.058
31. Chen Z, Bertin R, Froldi G (2013) EC50 estimation of antioxidant activity in DPPH* assay using several statistical programs. Food Chem 138:414–420. https://doi.org/10.1016/j.foodchem.2012.11.001
32. Kulisic T, Radonic A, Katalinic V, Milos M (2004) Use of different methods for testing antioxidative activity of oregano essential oil. Food Chem 85:633–640. https://doi.org/10.1016/j.foodchem.2003.07.024
33. Wojdyło A, Oszmiański J, Czemerys R (2007) Antioxidant activity and phenolic compounds in 32 selected herbs. Food Chem 105:940–949. https://doi.org/10.1016/j.foodchem.2007.04.038