{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,4,1]],"date-time":"2026-04-01T02:21:35Z","timestamp":1775010095399,"version":"3.50.1"},"reference-count":22,"publisher":"MDPI AG","issue":"2","license":[{"start":{"date-parts":[[2020,2,21]],"date-time":"2020-02-21T00:00:00Z","timestamp":1582243200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Pharmaceutics"],"abstract":"<jats:p>Triterpenes from the outer bark of birch have many beneficial biological and pharmacological activities. In particular, its wound healing efficacy is of paramount importance. Apart from that, particles of a birch bark dry extract aggregate into a three dimensional network when they are dispersed in lipids yielding a semi-solid oleogel. However, gel formation requires high amounts of the extract, which then acts at once as the active ingredient and the gelling agent. Infrared spectra of the respective mixtures proved that hydrogen bonds play a crucial role in the formation of the gel network. Dicarboxylic acids had almost no effect on gel strength. Monoalcohols increased the firmness of the oleogel with a decreasing effect from methanol &gt; ethanol &gt; butanol &gt; octanol. All tested terminal diols increased the gel strength whereas vicinal diols affected the gel strength negatively. The effect was highly dependent on their concentration. The different effects of the diols are linked to their structure and polarity. The most pronounced enhancement of gelation was found for 1,6-hexanediol, which reduced the amount of triterpene extract (TE), which is necessary for the formation of an oleogel by a factor of 10.<\/jats:p>","DOI":"10.3390\/pharmaceutics12020184","type":"journal-article","created":{"date-parts":[[2020,2,25]],"date-time":"2020-02-25T08:12:22Z","timestamp":1582618342000},"page":"184","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":9,"title":["Oleogels with Birch Bark Dry Extract: Extract Saving Formulations through Gelation Enhancing Additives"],"prefix":"10.3390","volume":"12","author":[{"given":"Kashif Ahmad","family":"Ghaffar","sequence":"first","affiliation":[{"name":"Department of Pharmaceutical Technology, Eberhard Karls University, Auf der Morgenstelle 8, 72076 Tuebingen, Germany"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-9553-0033","authenticated-orcid":false,"given":"Rolf","family":"Daniels","sequence":"additional","affiliation":[{"name":"Department of Pharmaceutical Technology, Eberhard Karls University, Auf der Morgenstelle 8, 72076 Tuebingen, Germany"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2020,2,21]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"394","DOI":"10.1039\/b515312n","article-title":"Pharmacological Activities of Natural Triterpenoids and Their Therapeutic Implications","volume":"23","author":"Dzubak","year":"2006","journal-title":"Nat. Prod. Rep."},{"key":"ref_2","first-page":"908","article-title":"The Pentacyclic Triterpenoids in Herbal Medicines and Their Pharmacological Activities in Diabetes and Diabetic Complications","volume":"20","author":"Alqahtani","year":"2012","journal-title":"Curr. Med. Chem."},{"key":"ref_3","doi-asserted-by":"crossref","unstructured":"Armbruster, M., M\u00f6nckedieck, M., Scherlie\u00df, R., Daniels, R., and Wahl, M. (2017). Birch Bark Dry Extract by Supercritical Fluid Technology: Extract Characterisation and Use for Stabilisation of Semisolid Systems. Appl. Sci., 7.","DOI":"10.3390\/app7030292"},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"1389","DOI":"10.1055\/s-2006-951723","article-title":"Physical, Chemical and Pharmacological Characterization of a New Oleogel-Forming Triterpene Extract from the Outer Bark of Birch (Betulae Cortex)","volume":"72","author":"Laszczyk","year":"2007","journal-title":"Planta Med."},{"key":"ref_5","unstructured":"Scheffler, A. (2013). Triterpene-Containing Oleogel-Forming Agent, Triterpene-Containing Oleogel and Method for Producing a Triterpene-Containing Oleogel. (8,536,380), U.S. Patent."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"742","DOI":"10.1134\/S1068162014070073","article-title":"Extraction of betulin from birch bark and study of its physico-chemical and pharmacological properties","volume":"40","author":"Kuznetsova","year":"2014","journal-title":"Russ. J. Bioorganic Chem."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"292","DOI":"10.4103\/0973-1296.137370","article-title":"Optimization of simultaneous ultrasonic-assisted extraction of water-soluble and fat-soluble characteristic constituents from Forsythiae Fructus Using response surface methodology and high-performance liquid chromatography","volume":"10","author":"Xia","year":"2014","journal-title":"Pharmacogn. Mag."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"153","DOI":"10.1016\/S0040-6031(02)00358-1","article-title":"Betulin isolation from birch bark by vacuum and atmospheric sublimation. A thermogravimetric study","volume":"398","author":"Guidoin","year":"2003","journal-title":"Thermochim. Acta"},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"535","DOI":"10.1248\/cpb.54.535","article-title":"Ceanothane- and Lupane-Type Triterpenes with Antiplasmodial and Antimycobacterial Activities from Ziziphus cambodiana","volume":"54","author":"Suksamrarn","year":"2006","journal-title":"Chem. Pharm. Bull."},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"e0159430","DOI":"10.1371\/journal.pone.0159430","article-title":"Isolation, Characterization and Anticancer Potential of Cytotoxic Triterpenes from Betula utilis Bark","volume":"11","author":"Mishra","year":"2006","journal-title":"PLoS ONE"},{"key":"ref_11","unstructured":"(2020, February 20). EMA: Marketing Authorisation Episalvan. Available online: https:\/\/www.ema.europa.eu\/en\/medicines\/human\/EPAR\/episalvan."},{"key":"ref_12","first-page":"572","article-title":"Evaluation of the mechanism of gelation of an oleogel based on a triterpene extract from the outer bark of birch","volume":"68","author":"Grysko","year":"2013","journal-title":"Die Pharm."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"13664","DOI":"10.1021\/acs.langmuir.5b03730","article-title":"Hierarchical Self-Assembly of a Renewable Nanosized Pentacyclic Dihydroxy-triterpenoid Betulin Yielding Flower-Like Architectures","volume":"31","author":"Bag","year":"2015","journal-title":"ACS Langmuir"},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"4564","DOI":"10.1039\/c1nr10886g","article-title":"First self-assembly study of betulinic acid, a renewable nano-sized, 6-6-6-6-5 pentacyclic monohydroxy triterpenic acid","volume":"3","author":"Bag","year":"2011","journal-title":"Nanoscale"},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"221","DOI":"10.1016\/j.cocis.2007.07.002","article-title":"Structuring edible oils by alternatives to crystalline fat","volume":"12","author":"Pernetti","year":"2007","journal-title":"Curr. Opin. Colloid Interface Sci."},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"417","DOI":"10.1007\/s11746-003-0714-0","article-title":"Organogelation of Plant Oils and Hydrocarbons by Long-Chain Saturated FA, Fatty Alcohols, Wax Esters, and Dicarboxylic Acids","volume":"80","author":"Daniel","year":"2003","journal-title":"J. Am. Oil Chem. Soc."},{"key":"ref_17","doi-asserted-by":"crossref","unstructured":"Patel, A. (2018). Edible Oil Structuring: Concepts, Methods and Applications, The Royal Society of Chemistry.","DOI":"10.1039\/9781788010184"},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"43","DOI":"10.1016\/0928-4931(95)00102-6","article-title":"Lecithin bridging by hydrogen bonds in the organogel","volume":"3","author":"Shchipunov","year":"1995","journal-title":"Mater. Sci. Eng. C"},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"6089","DOI":"10.1039\/c2cs35106d","article-title":"Supramolecular gels formed from multi-component low molecular weight species","volume":"41","author":"Buerkle","year":"2012","journal-title":"Chem. Soc. Rev."},{"key":"ref_20","first-page":"485","article-title":"Transferable Intermolecular Potentials for Carboxylic Acids and Their Phase Behavior","volume":"56","author":"Vahid","year":"2010","journal-title":"Thermodynamics"},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"2153","DOI":"10.1021\/acs.jpcb.6b10652","article-title":"On the Dimerization of Carboxylic Acids: An Equation of State Approach","volume":"121","author":"Tsivintzelis","year":"2017","journal-title":"J. Phys. Chem. B"},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"2293","DOI":"10.1039\/b921488g","article-title":"Aggregation, ageing and transport properties of surface modified fumed silica dispersions","volume":"6","author":"Matic","year":"2010","journal-title":"Soft Matter"}],"container-title":["Pharmaceutics"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1999-4923\/12\/2\/184\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T08:59:47Z","timestamp":1760173187000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1999-4923\/12\/2\/184"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2020,2,21]]},"references-count":22,"journal-issue":{"issue":"2","published-online":{"date-parts":[[2020,2]]}},"alternative-id":["pharmaceutics12020184"],"URL":"https:\/\/doi.org\/10.3390\/pharmaceutics12020184","relation":{},"ISSN":["1999-4923"],"issn-type":[{"value":"1999-4923","type":"electronic"}],"subject":[],"published":{"date-parts":[[2020,2,21]]}}}