Formulation and Antioxidant Activity Test of Centella asiatica Herba Extract and Moringa oleifera Leaves Extract as An Anti-Aging Emulgel

Main Article Content

Ni M.D.S Suena
Luh R.P Rahayu
Santi C. Wijaya
Ni P.U Antari
Ketut A. Adrianta

Abstract

Asiaticoside in Centella asiatica L. and β-sitosterol in Moringa oleifera exhibit antioxidant properties, making them potential active ingredients in anti-aging formulations. Emulgel, a combination of emulsion and hydrogel systems, offers specialized structures that enhance the stability of delivery systems or bioactive ingredients. Proper excipients, including emulsifiers, bases, and gelling agents like Carbopol 940 and stearic acid, are crucial for maintaining emulgel stability. This study aimed to optimize Carbopol and stearic acid concentrations in an emulgel formula containing Gotu kola and Moringa leaf extracts for optimal physical quality and antioxidant activity. Three emulgel formulas (F1: 0.5% Carbopol; 4% stearic acid, F2: 1% Carbopol; 3.5% stearic acid, F3: 1.5% Carbopol; 3% stearic acid) were tested for organoleptic properties, homogeneity, pH, centrifugation, spreadability, adhesion, hedonic response, and antioxidant activity (measured using the DPPH technique). All formulas showed changes in shape and minor oil appearance during centrifugation, indicating texture instability due to low emulsion system stability. Despite this, all formulations were homogeneous with stable pH, spreadability, and adhesion. Panelists favored F1 followed by F3, with none preferring F2 in hedonic tests.
Emulgel F1 demonstrated optimal physical quality and panelist preference, while emulgel F3, with the lowest stearic acid concentration (3%), exhibited the highest antioxidant activity. Emulgel F3 holds promise for further development as an anti-aging cosmetic product, combining superior physical quality with high antioxidant efficacy.

Article Details

How to Cite
Suena, N. M., Rahayu, L. R., Wijaya, S. C., Antari, N. P., & Adrianta, K. A. (2024). Formulation and Antioxidant Activity Test of Centella asiatica Herba Extract and Moringa oleifera Leaves Extract as An Anti-Aging Emulgel. Tropical Journal of Natural Product Research (TJNPR), 8(3), 6525-6536. https://doi.org/10.26538/tjnpr/v8i3.9
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References

Eftekhari A, Dizaj SM, Chodari L, Sunar S, Hasanzadeh A, Ahmadian E, Hasanzadeh M. The promising future of nanoantioxidant therapy against environmental pollutants induced-toxicities. Biomed Pharmacother. 2018;103:1018–27.

Song Q, Zhou X, Xu K, Liu S, Zhu X, Yang J. The Safety and Antiaging Effects of Nicotinamide Mononucleotide in Human Clinical Trials: an Update. Adv Nutr [Internet]. 2023. Available from: https://doi.org/10.1016/j.advnut.2023.08.008

Sohail M, Muhammad Faran Ashraf Baig M, Akhtar N, Chen Y, Xie B, Li B. Topical lycopene emulgel significantly improves biophysical parameters of human skin. Eur J Pharm

Biopharm. 202; 180:281–8.

Burke KE. Protection From Environmental Skin Damage With Topical Antioxidants. Clin Pharmacol Ther. 2019; 105(1):36–8.

Cefali LC, Vazquez C, Ataide JA, Figueiredo MC, Ruiz ALTG, Foglio MA, Lancellotti M, Mazzola PG. In vitro activity and formulation of a flavonoid-containing cashew pulp extract for the topical treatment of acne and the protection of skin against premature aging. Nat Prod Res. 2021;35(23):5243–9.

Ong TS, Chu CC, Tan CP, Nyam KL. Preparation and Evaluation of Pumpkin Seed Oil-based Vitamin E Cream Formulations for Topical Application. J Oleo Sci. 2020;69(4):297–306.

Cefali LC, Franco JG, Nicolini GF, Ataide JA, Mazzola PG. In vitro antioxidant activity and solar protection factor of blackberry and raspberry extracts in topical formulation. J

Cosmet Dermatol. 2019;18(2):539–44.

Suman D, Sangeeta S, Beena K. Emugel for topical drug delivery: A novel approach. GSC Biol Pharm Sci. 2020;11(3):104–14.

Chauhan L, Gupta S. Creams: A Review on Classification, Preparation Methods, Evaluation and its Applications. J Drug Deliv Ther. 2020;10(5-s):281–9.

Hemalatha B, Priya TP, Manasa K, Greeshmika C, Kavya P, Sayeeda SS, Padmalatha K. Optimization of Oxiconazole Topical Emulgel Formulation for the Treatment of Skin

Infections. Asian J Pharm Technol. 2022;232–6.

Light K, Karboune S. Emulsion, hydrogel and emulgel systems and novel applications in cannabinoid delivery: a review. Crit Rev Food Sci Nutr. 2022;62(29):8199–229.

Yadav SK, Mishra MK, Tiwari A, Shukla A. Emulgel: A New Approach for Enhanced Topical Drug Delivery. Int J Curr Pharm Res. 2017;9(1):15–9.

Raj ELPS, Balakrishnan S. Short Review - Emulgel. J Compr Pharm. 2016;03(01):34–7.

Patel N, Chaudhary S, Chaudhary A. Emulgel –Emerging as a Smarter Value-Added Product Line Extension for Topical Preparation. Indo Glob J Pharm Sci. 2022;12:92–103.

Safitri FI, Nawangsari D, Febrina D. Overview: Application of Carbopol 940 in Gel. In: Proceedings of the International Conference on Health and Medical Sciences (AHMS 2020). Paris, France: Atlantis Press; 2021. p. 80–4. Available from: https://www.atlantis-press.com/article/125951906

Sheskey PJ, Cook WG, Cable CG. Handbook of Pharmaceutical Excipients [Internet]. 8th ed. Sheskey PJ, Cook WG, Cable CG, editors. London; Washington DC.: Pharmaceutical Press and American Pharmacist Association; 2017. 1216 p. Available from:

https://www.pharmpress.com/product/9780857113757/excipients

de Souza Ferreira SB, Bruschi ML. Investigation of the physicochemical stability of emulgels composed of poloxamer 407 and different oil phases using the Quality by Design approach. J Mol Liq. 2021; 332:115856. Available from: https://doi.org/10.1016/j.molliq.2021.115856

Raharjo AB, Putra RDA, Indayaningsih N, Srifiana Y, Hardiansyah A, Irmawati Y, Widodo H, Destyorini F. Preparation of polyvinyl alcohol/asiaticoside/chitosan membrane nano-composite using electrospinning technique for wound dressing. In: the 5th International Symposium on Frontier of Applied Physics (ISFAP 2019). Tangerang Selatan: AIP Publishing; 2020. p. 030023. Available from: https://pubs.aip.org/aip/acp/article/962793

Amalia N, Okta FN, Zahra AA, Nuari DA. Update Review: Extraction, Purification, and Pharmacological Activities of Gotu Kola Terpenoids. Lett Appl NanoBioScience.

;13(1):1–17.

Salem MI, El-Sebai A, Elnagar SA, Abd El-hady AM. Evaluation of lipid profile, antioxidant and immunity statuses of rabbits fed Moringa oleifera leaves. AsianAustralasian J Anim Sci. 2020;DOI:10.5713/ajas.20.0499

Farooq B, Koul B, Mahant D, Yadav D. Phytochemical Analyses, Antioxidant and Anticancer Activities of Ethanolic Leaf Extracts of Moringa oleifera Lam. Varieties. Plants. 2021;10(11):2348. Available from: https://www.mdpi.com/2223-7747/10/11/2348

Arivarasu L. In-Vitro Antioxidant Potential of BetaSitosterol: A Preface. Cureus. 2023;15(9). Available from: https://www.cureus.com/articles/185526-in-vitroantioxidant-potential-of-beta-sitosterol-apreface

Thien DB, Nghia ND, Boi VN, Tuyen DTT, Cuong DX, Thuan PT, Hien VTT, Trinh PT, Hien DV. The content of polyphenol and chlorophyll, and antioxidant activity of Centella asiatica: Accumulation according to the growth times and their correlation. Sapporo Med J. 2021;55(6):1–8.

Lin M, Zhang J, Chen X. Bioactive flavonoids in Moringa oleifera and their health-promoting properties. J Funct Foods. 2018;47:469–79.

Nurulita NA, Sundhani E, Amalia I, Rahmawati F, Nurhayati N, Utami D. Antioxidant and Anti-aging activity of MoringaLeaves Extract Body Butter. J Ilmu Kefarmasian Indones.

;17(1):1.

Hossain MA, Disha NK, Shourove JH, Dey P. Determination of Antioxidant Activity and Total Tannin from Drumstick (Moringa oleifera Lam.) Leaves Using Different Solvent

Extraction Methods. Turkish J Agric - Food Sci Technol. 2020;8(12):2749–55.

Crespo YA, Bravo Sánchez LR, Quintana YG, Cabrera AST, Bermúdez del Sol A, Mayancha DMG. Evaluation of the synergistic effects of antioxidant activity on mixtures of the

essential oil from Apium graveolens L., Thymus vulgaris L. and Coriandrum sativum L. using simplex-lattice design. Heliyon. 2019;5(6):e01942.

Das A, Kalita A, Raychaiudhuri U, Chakraborty R. Synergistic effect of herbal plant extract (Hibiscus sabdariffa) in maintain the antioxidant activity of decaffeinated green tea from various parts of Assam. J Food Sci Technol. 2019;56(11):5009–16.

Zhang D, Liu J, Ruan J, Jiang Z, Gong F, Lei W, Wang X, Zhao J, Meng Q, Xu M, Tang J, Li H. Combination of millet pepper and garlic water extracts improves the antioxidant

capability of myofibrillar protein under malondialdehydeinduced oxidative modification. LWT. 2023;174:114472.

Benamar-Aissa B, Gourine N, Ouinten M, Harrat M, Benarfa A, Yousfi M. Synergistic effects of essential oils and phenolic extracts on antioxidant activities responses using

two Artemisia species (A. campestris and A. herba alba) combined with Citrus aurantium. Biocatal Agric Biotechnol. 2023;47:102570.

Reubun YTA, Kumala S, Setyahadi S, Simanjuntak P. Inhibition of Acetylcolinesterase Enzyme from Pegagan Herb Extract (Centella asiatica), Kelor Leaf (Moringa oleifera) Extract and Combinations. J Pharm Appl Chem. 2021;7(1):33–6.

Subaidah WA, Andayani Y, Ayu D, Kumaradewi P. Emulgel formulation of wild cherry leaves (Antidesma bunius L. Spreng) extract and its antioxidant activity. 2022;10(2):1–5.

Ayunin Q, Miatmoko A, Soeratri W, Erawati T, Susanto J, Legowo D. Improving the anti-ageing activity of coenzyme Q10 through protransfersome-loaded emulgel. Sci Rep.

;12(1):906.

Iskandar B, Novita G, Fitri Annisa F, Leny L, Hafiz I, Surboyo MDC, Lee C. Evaluation of Physical Quality and Antioxidant Activity of Ethanol Extract of Moringa Leaves (Moringa oleifera LAM) Formulated in Emulgel Preparation. Res J Pharm Technol. 2022;15(6):2703–8.

Wu L, Li L, Chen S, Wang L, Lin X. Deep eutectic solventbased ultrasonic-assisted extraction of phenolic compounds from Moringa oleifera L. leaves: Optimization, comparison and antioxidant activity. Sep Purif Technol. 2020;247:117014.

Shah RS. Formulation and Evaluation of Turmeric Emulgel. Asian J Pharm Technol. 2021;11(3):213–9.

Pertiwi D, Hafiz I, Jannah W, Winata HS, Sari M, Suroyo RB. Antibacterial Activities of Belimbing Wuluh (Averrhoa bilimbi L.) Ethyl Acetate Extract on Gel Formulated Against

Propionibacterium acnes and Staphylococcus aureus. Int J Appl Pharm. 2020;12(6):224–8.

Mardikasari SA, Akib N, Suryani S. Formulasi dan Uji Stabiltias Krim Asam Kojat dalam Pembawa Vesikel Etosom. Maj Farm dan Farmakol [Internet]. 2020;24(2):49–53.

Strus O, Polovko N, Plaskonis Y. The Investigation of the Development of a Cream Composition with the Sapropel Extract. Asian J Pharm Clin Res. 2018;11(7):147.

PH Meter Vs PH Paper: Which One Do You Need?. Atlas Scientific Environmental Robotics. 2021. Available from: https://atlas-scientific.com/blog/ph-meter-vs-ph-paperwhich-one-do-you-need/#:~:text=Advantages Of Using pH Paper,%2C wherever you’re testing.

Cendana Y, Adrianta KA, Suena NMDS. Sandalwood (Santalum album L.) Essential Oil Spray Gel Formulation as One of the Anti-inflammatory Preparation Candidates. J Ilm Medicam. 2021;7(2):84–9.

Istiqomah N, Akuba J. Formulasi Emulgel dari Ekstrak Daun Kelor (Moringa oleifera LAM) serta Evaluasi Aktivitas Antioksidan dengan Metode DPPH. J Syifa Sci Clin Res. 2021;3(1):9–18.

Sekaran U, Bougie R. Research Methods For Business: A Skill Building Approach. Seventh Ed. Hoboken, New Jersey: Wiley; 2016. 448 p.

Setyaningsih D, Wijayanti PL, Muna N. Application of Mono-Diacyl Glycerol from Palm Oil By Product as Emulsifier for Body scrub. IOP Conf Ser Earth Environ Sci. 2018;209(1):012047.

Suena NMDS, Antari NPU. Uji Aktivitas Antioksidan Maserat Air Biji Kopi (Coffea Canephora) Hijau Pupuan dengan Metode DPPH (2, 2-difenil-1-pikrilhidrazil). J Ilm

Medicam. 2020;6(2):111–7.

Brás T, Neves LA, Crespo JG, Duarte MF. Effect of extraction methodologies and solvent selection upon cynaropicrin extraction from Cynara cardunculus leaves. Sep Purif Technol. 2020;236:116283.

Sasadara MM V, Wirawan IGP. Effect of extraction solvent on total phenolic content, total flavonoid content, and antioxidant activity of Bulung Sangu (Gracilaria sp.) Seaweed. IOP Conf Ser Earth Environ Sci. 2021;712(1):012005.

Nafiunisa A, Aryanti N, Wardhani DH. Kinetic Study of Saponin Extraction from Sapindus rarak DC by UltrasoundAssisted Extraction Methods. Bull Chem React Eng Catal. 2019;14(2):468.

Kementrian Kesehatan RI. Farmakope Herbal Indonesia Edisi II Tahun 2017. Directorate General of Pharmaceuticals and Health Devices. 2017. p. 212; 350.

Apriyati E, Murdiati A, Triwitono P. Effect of Maceration Time on Flavonoid Levels and Antioxidant Activity of Moringa Leaf Extract. J Teknol Pangan. 2022;16(1):116–23.

Yahya MA, Nurrosyidah IH. Antioxidant activity ethanol extract of gotu kola (Centella asiatica (L.) Urban) with DPPH method (2,2-Diphenyl-1-Pikrilhidrazil). J Halal Prod Res. 2020;3(2):106.

Fathordoobady F, Mirhosseini H, Selamat J, Manap MYA. Effect of solvent type and ratio on betacyanins and antioxidant activity of extracts from Hylocereus polyrhizus flesh and peel by supercritical fluid extraction and solvent extraction. Food Chem. 2016;202:70–80.

Ajazuddin, Alexander A, Khichariya A, Gupta S, Patel RJ, Giri TK, Tripathi DK. Recent expansions in an emergent novel drug delivery technology: Emulgel. J Control Release.

;171(2):122–32.

Khan BA, Ali A, Hosny KM, Halwani AA, Almehmady AM, Iqbal M, Alharbi WS, Abualsunun WA, Bakhaidar RB, Murshid SSA, Khan MK. Carbopol emulgel loaded with ebastine for urticaria: development, characterization, in vitro and in vivo evaluation. Drug Deliv. 2022 ;29(1):52–61.

Deng Y, Dai M, Wu Y, Peng C. Emulsion system, demulsification and membrane technology in oil–water emulsion separation: A comprehensive review. Crit Rev Environ Sci Technol. 2023;53(12):1254–78.

Hu YT, Ting Y, Hu JY, Hsieh SC. Techniques and methods to study functional characteristics of emulsion systems. J Food Drug Anal. 2017;25(1):16–26.

Pereira RCL, Carvalho RM, Couto BC, De Oliveira MCK, Eberlin MN, Vaz BG. Waxy crude oil emulsion gel: Chemical characterization of emulsified phase extract components. Energy and Fuels. 2014;28(12):7352–8.

Bouhoute M, Taarji N, Vodo S, Kobayashi I, Zahar M, Isoda H, Nakajima M, Neves MA. Formation and stability of emulsions using crude extracts as natural emulsifiers from

Argan shells. Colloids Surfaces A Physicochem Eng Asp. 2020;591:124536. DOI: 10.1016/j.colsurfa.2020.124536

McClements DJ, Jafari SM. Improving emulsion formation, stability and performance using mixed emulsifiers: A review. Adv Colloid Interface Sci. 2018;251:55–79.

Čižinauskas V, Elie N, Brunelle A, Briedis V. Skin Penetration Enhancement by Natural Oils for Dihydroquercetin Delivery. Molecules. 2017;22(9):1536.

Cowley A. The effect of selected natural oils on the permeation of flurbiprofen through human skin. North-West University, Potchefstroom Campus; 2012.

Angelina C, Swasti YR, Pranata FS. Increased Nutritional Value of Food Products with the Addition of Moringa Leaf Powder: A Review. J Agroteknologi. 2021;15(01):79.

Idris FN, Nadzir MM. Comparative studies on different extraction methods of Centella asiatica and extracts bioactive compounds effects on antimicrobial activities. Antibiotics. 2021;10(4). DOI: 10.3390/antibiotics10040457

Pratiwi L, Fudholi A, Martien R, Pramono S. Physical and Chemical Stability Test of SNEDDS (Self-nanoemulsifying Drug Delivery System) and Nanoemulsion Ethyl Acetate

Fraction of Garcinia mangostana L. Maj Obat Tradis. 2018;23(2):84.

Lukić M, Pantelić I, Savić SD. Towards Optimal pH of the Skin and Topical Formulations: From the Current State of the Art to Tailored Products. Cosmetics. 202;8(3):69. DOI:

3390/cosmetics8030069

Adrianta KA, Yuda PESK, Purnamasari PS, Suena NMDS. Jackfruit (Artocarpus heterophyllus Lamk) Leaf as a Natural Sun Stick Protector Through the Inhibition of the MMP-1 Receptor. Trop J Nat Prod Res. 2023;7(5):2952–8. A

Vázquez-Blanco S, González-Freire L, Dávila-Pousa MC, Crespo-Diz C. pH determination as a quality standard for the elaboration of oral liquid compounding formula. Farm Hosp.

;42(6):221–7.

Rani Z, Ridwanto R, Nasution HM, Kaban VE, Nasri N, Karo NB. Antibacterial activity of freshwater lobster (Cherax quadricarinatus) shell chitosan gel preparation against Escherichia coli and Staphylococcus aureus. J Appl Pharm Sci. 2022;13(2):146–53.

Sari NKK, Suradnyana IGM, Suena NMDS. Physical Stability Test of Body Butter Macerate Green Coffee Bean Water (Coffea canephora) at Cool Temperature. J Farm Higea. 2021;13(2):79.

Ratnah S, Salasa AM, Ramadhan DSF. Formulation, Physical Quality, and Microbial Contamination Tests of Anti-Acne Cream from Longan (Euphoria longan [Lour. Steud.]) Seed Extract. Trop J Nat Prod Res. 2023;7(7):3297–305.

Okoro NK, Oseni BA, Okubanjo OO, Adegun AA, Ilomuanya MO. Development of Diclofenac and Capsaicin Emulgel for the Management of Inflammation in Rheumatoid Arthritis. Trop J Nat Prod Res. 2023;7(6):3246–52.

Rismawati D, Aji N, Herdiana I. The Effect of Butylated Hydroxyanisole on The Stability and Characteristics of Emulgel Combination Red Ginger Extract-Peppermint Oil. Pharmaqueous J Ilm Kefarmasian. 2020;1(2):35–42.

Yahaya ZS, Otaru LO, Mohammed BB, Adeleye OA, Dagogot NC, Abdullahi I. Evaluation of diclofenac emulgel prepared with sesame oil as a lipophilic carrier. Trop J Pharm Res. 2023;22(9):2021–7.

Mudhana AR, Pujiastuti A. Effect of Triethanolamine and Stearic Acid on Physical Quality and Mechanical Stability of Tomato Juice Cream. Indones J Pharm Nat Prod [Internet]. 2021 Dec 31;4(2):113–22.

Suhesti TS, Rohman MMH, Sunarto S. Formulation of Gel Hand Sanitizer of Nagasari Leaf Extract (Mesua ferrea L.). Indones J Pharm Sci Technol. 2022 ;1(1):31. Available from:

http://jurnal.unpad.ac.id/ijpst/article/view/36465

Lumentut N, Edi HJ, Rumondor EM. Formulation and Physical Stability Test of Ethanol Extract Cream Preparation of Goroho Banana Peel (Musa acuminafe L.) Concentration

5% as Sunscreen. J MIPA. 2020;9(2):42. Available from: https://ejournal.unsrat.ac.id/index.php/jmuo/article/view/28248

Mardhiani YD, Supriadi D, Islamiyah PHN. Formulation and Evaluation of Sunscreen Gel Combination of Bisoctrizole and Gotu Kola Extract (Centella asiatica (L.) Urban). Indones J Pharm. 2023;4(3):31–41.

Sumule A, Kuncahyo I, Leviana F. Optimization of Carbopol 940 and Glycerin in Snail Slime Gel Formula (Achatina fulica Ferr) as Antibacterial Staphylococcus aureus using the

Simplex Lattice Design Method. Pharm J Farm Indones (Pharmaceutical J Indones. 2020;17(1):108.

Lestari PM, Supandi, Nusafitri M. Ethanol Extract Emulgel 96% Brokatul Rice (Oryza sativa L.) as Antioxidant. IOP Conf Ser Earth Environ Sci. 2021;755(1):012017. Available from: https://iopscience.iop.org/article/10.1088/1755-1315/755/1/012017

Kuspradini H, Wulandari I, Putri AS, Tiya SY, Kusuma IW. Phytochemical, antioxidant and antimicrobial properties of Litsea angulata extracts. F1000Research [Internet]. 2018

Nov 22;7:1839. Available from: https://f1000research.com/articles/7-1839/v1

Hasibuan F., Syahfitri W, Ilyas S, Hutahaean S. Phytochemical screening, antioxidant activity and thin-layer chromatography test of methanol extract and simplicia leaves

of loquat (Eriobotrya japonica Lindl). IOP Conf Ser Mater Sci Eng . 2020 ;725(1):012069. Available from: https://iopscience.iop.org/article/10.1088/1757-899X/725/1/012069

Nayaka NMDMW, Fidrianny I, Sukrasno, Hartati R, Singgih M. Antioxidant and antibacterial activities of multiflora honey extracts from the Indonesian Apis cerana bee. J Taibah Univ Med Sci [Internet]. 2020;15(3):211–7.

Bastante CC, Cardoso LC, Serrano CM, Ossa EJM de la. Supercritical impregnation of food packaging films to provide antioxidant properties. J Supercrit Fluids. 2017;128:200–7.

Destrina HP. Effect of Varying Concentrations of Carbopol 940 Base on the Physical-Chemical Properties and Antioxidant Activity of Jackfruit (Artocarpus heterophyllus)

Leaf Extract Gel Preparations. Universitas Wahid Hasyim; 2018. Available from:

http://eprints.unwahas.ac.id/id/eprint/1482

Aji Pangestu RW, Aisiyah S, Harmastuti N. Optimasi Karbopol dan Gliserin pada Sediaan Gel Dispersi Padat Ibuprofen Secara Simplex Lattice Design. J Farm (Journal Pharmacy). 2021;9(2):5–14.

Deuschle VCKN, Deuschle RAN, Bortoluzzi MR, Athayde ML. Physical chemistry evaluation of stability, spreadability, in vitro antioxidant, and photo-protective capacities of topical formulations containing Calendula officinalis L. leaf extract. Brazilian J Pharm Sci. 2015;51(1):63–75.

Athikomkulchai S, Tunit P, Tadtong S, Jantrawut P, Sommano SR, Chittasupho C. Moringa oleifera Seed Oil Formulation Physical Stability and Chemical Constituents for Enhancing Skin Hydration and Antioxidant Activity. Cosmetics. 2020;8(1):2. Available from:

https://www.mdpi.com/2079-9284/8/1/2

Aulton ME, Taylor K. Aulton’s pharmaceutics : the design and manufacture of medicines. 5th ed. Taylor K, Aulton M, editors. London: Elsevier; 2018. 933 p.

Binder L, Mazál J, Petz R, Klang V, Valenta C. The role of viscosity on skin penetration from cellulose ether‐based hydrogels. Ski Res Technol. 2019;25(5):725–34.