High solubility and stability of artemisinin in aqueous infusions
L'artemisinine est soluble et stable dans l'eau
For 30 years, it was claimed that Artemisia annua tea infusions could not be used as remedy because artemisinin was barely soluble in water. The “WHO Position Statement on Effectiveness of Non-tablet Forms of Artemisia annua L against Malaria “, present for long years on the WHO site, not dated, not signed, not refenced, bluntly states: “it is virtually impossible for a tea bag to contain the amount of substance required to cure malaria. Artemisinin … is unstable when heated. Boiling water to make tea may cause it to lose any anti-malarial properties it may have”. Coming from an international body like WHO it was accepted by everybody as true. But it is wrong! And the need to produce water soluble derivatives of artemisinin a loss of time and energy. But it guaranteed a huge market. A review paper published by Frank van der Kooy revived our interest in the question why the solubility of artemisinin is higher in Artemisia annua infusions than for the pure substance in distilled water. Frank van der Kooy, Robert Verpoorte. The content of artemisinin in the Artemisia annua tea infusion. Planta Med 2011 Oct 3;77(15):1754-6. Epub 2011 Dec 3. We quote: « It is possible that the compounds responsible for the enhanced aqueous solubility of artemisinin only occur in the stems and not in the leaves…Furthermore, no studies have been conducted on the possible chemical reactions that can take place or the extraction efficiency of urine, as this was the common extraction solvent in ancient times. This interaction between common water ions and salts, and also common metabolites present in urine, should be further investigated and its effect on the various biological activities ascribed to Artemisia annua ». Sodium bicarbonate also enhance the extraction of tannins from medicinal herbs. The feature is used in Turkish tea houses. Some bicarbonate is added to the water used for ddecoction and the infusion becomes darker. E Moroydor Derun, T Yalcin S Piskin. The effect of sodium bicarbonate on the Mg and P concentrations in Turkish black and green tea. Int J Scholarly and Scientific Res and Innov, 2014, 8, 557-559 Extraction efficiencies for artemisinin of greater than 70% have been noticed. The authors propose that the solubility of artemisinin is enhanced by the action of other constituents present in Artemisia annua. Räth K, Taxis K, Walz G, Gleiter CH, Li SM, Heide L. Pharmacokinetic study of artemisinin after oral intake of a traditional preparation of Artemisia annua L. (annual wormwood). Am J Trop Med Hyg. 2004 Feb;70(2):128-32. Along these lines a paper from Tehran studying the effect of surfactants on extraction of polyphonic compounds shows indeed that surfactants in water give a much higher extraction of polyphenols than methanol in water. Saponins present in Artemisiaa act as surfactants. The authors also studied the influence of ionic strength and pH. A 2% potassium chloride solution in water was determined to be the optimum salt concentration for the extraction, even higher as with the surfactant. It is possible that osmotic pressure plays a role in the rupture of plant cells. This needs to be investigated. Artemisia plants are very rich in potassium up to 26 000 ppm, much more than other plants (see below) Reza Hosseinzadeh, Khatereh Khorsandi, Syavash Hemmaty. Study of the Effect of Surfactants on Extraction and Determination of Polyphenolic Compounds and Antioxidant Capacity of Fruits Extracts. PlosONE, 2013, 8(3) e57353 A study from Italy comes to the same conclusion: artemisinin present in the tea is probably co-solubilized with other ingredients, some of which have also antimalarial activity. A De Donno, T Grassi, A Idolo, FP Fanizzi. First-time comparison of the in vitro antimalarial activity of Artemisia annua herbal tea and artemisinin. Trans Royal Soc Trop Med Hyg, 2012, 106, 696-700 More important even could be the work we have done in partnership with the University of Al Quds, Jerusalem, Palestine. For several medicinal herbs including Artemisia species, they find that when the extraction in done by hot water containing NaCl or sodium bicarbonate, the beta-hematin inhibition effect is strongly enhanced. Akkawi M, Jaber S, Abu-Remeleh Q, Engeu OP, Lutgen P (2014). Investigations of Artemisia Annua and Artemisia Sieberi Water Extracts Inhibitory Effects on β-Hematin Formation. Med Aromat Plants 3: 150. doi: 10.4172/2167-0412.1000150 Suhair Jaber, Saleh Abu-Lafi, Pierre Lutgen, Mutaz Qutob, Qassem Abu-Remeleh and Mutaz Akkawi. Bicarbonate In-Vitro Effect on Beta-Hematin Inhibition by Artemisia sieberi Aqueous Infusion. Journal of Pharmacy and Pharmacology 3 (2015) 63-72 doi: 10.17265/2328-2150/2015.02.003 The effect of sodium bicarbonate is negligible if it is added to the infusion after extraction. This is the case for all salts dissolved in pure water: NaCl, KBr, NaNO3, KCl, ZnCl2, KI, K2HPO4): they have no effect per se on beta-hematin inhibition (personal communication from M Akkawi). The poor aqueous solubility of drugs is an industry wide problem. Some approaches have even been patented. Ravula Prasad, Solid lipid dispersion for aqueous solubility enhancement of poorly water soluble drugs, WO 2010143199 A1 Addition of bicarbonates will cause dehydration of cell ducts by an osmose like effect, so ducts will dry then explode to release their content. The use of urine for efficient extraction of medicinal herbs may rely on similar elements. Urine contains 1% of chlorides. It also contains 1 gm per liter of sodium bicarbonate, or more if the pH of urine is > 7 and it contains much more potassium than sea water. JL Gamble, Carbonate and bicarbonate in urine. J Biol Chem. 1922, 51, 299-3 Bicarbonate contents are much higher in roots and stems than in leaves. A. Wallace. T. Mueller. A. WooS. M. Soufi. Plant uptake of bicarbonate as measured with the11C isotope. Plant and Soil. April 1979, Volume 51, Issue 3, pp 431–435 Artemisia plants are rich in the ambiphilic surfactant saponin. Based on literature data on vegetables and medicinal plants our best estimate for saponins in Artemisia plants is around 1% versus 0.4 % in vegetables. There are many anecdotical claims that Artemisia annua stems are richer in saponins than leaves. The problem is that it is very difficult, even impossible to find quantitative studies on saponins in any Artemisia species. Among all the medicinal plants those of the Artemisia family have the highest potassium content. The first to report this was the USDA. E Brisibe, E. Umoren, Pedro M. Magalhäes ,Jorge F.S. Ferreira. Nutritional characterisation and antioxidant capacity of different tissuesof Artemisia annua L. Food Chemistry, 2008, 115, 1240-46 Potassium concentrations in Artemisia annua are 10 to 100 times higher than those of other minerals, particularly sodium. A study in Morocco measured the potassium content of four medicinal plants. For Artemisia herba alba it is the highest B. Imelouane, M. Tahri , M. Elbastrioui, F. Aouinti, A. Elbachiri. Mineral Contents of Some Medicinal and Aromatic Plants Growing in Eastern Morocco J. Mater. Environ. Sci. 2 (2) (2011) 104-111 Imelouane et al.104 A more complete study in Pakistan, comparing 10 medicinal plants finds that potassium content in Artemisia annua is the highest. This goes along with an exceptionally high concentration of HCO₃¯ bicarbonate. Iqbal Hussain. Evaluation of Inorganic Profile of Selected Medicinal Plants of Khyber Pakhtunkhwa Pakistan. World Applied Sciences Journal 12 (9): 1464-1468, 2011 Other studies have shown that foods simultaneously rich in potassium and bicarbonate have very positive health effects, especially against osteoporosis, renal stones and hypertension. Milk products are rich in potassium but poor in bicarbonate. Many fruits and vegetables combine both; coffee and wine also offer this combination SA Lanham-New. The balance of bone health: tipping the scales in favor of potassium-rich, bicarbonate rich foods. The Journal of Nutrition, 2008, 138, 172-177 Michele Barbera, Mauro Barbera, Quintino Paola. The importance of potassium citrate and potassium bicarbonate in the treatment of uric renal stones. Congress Scientia 2016, 88, 4, Often the concentration of potassium is higher in stems than in leaves, in artichoke for example, in rice, in tomatoes. Christian Gary, Nadia Bertin, Jean-Sylvain Frossard and Jacques Le Bot. High mineral contents explain the low construction cost of leaves, stems and fruits of tomato plants Journal of Experimental Botany, Vol. 49, No. 318, pp. 49–57, January 1998. The presence of proanthocyanidins in Artemisia plants may also explain the surprisingly high solubility of artemisinin in tea infusions. And the solubility of resveratrol in wine and not in pure water. Jackson JK, Letchford K. The Effective Solubilization of Hydrophobic Drugs Using Epigallocatechin Gallate or Tannic Acid-Based Formulations. J Pharm Sci. 2016 Oct;105(10):3143-52. doi: 10.1016/j.xphs.2016.06.027. Why and how these constituents of Artemisia annua enhance the solubility of lipophilic constituents needs further investigation. The work of Frank van der Kooy (op.cit.) has shown that the extraction is up to 80% if the dried herb is in contact with boiling water for 2-5 minutes. The addition of a very small amount of salt or bicarbonate before pouring the boiling water will strengthen the infusion. The stability of artemisinin in Artemisia annua leaves has been determined in several laboratories for periods up to five years (personal communications) in evident contradiction with the OMS position statement. A work from South Africa even shows that the antioxidant properties of Artemisia afra stay constant for at least 12 years. SO Amoo, AO Aremu, M Moyo, J van Staden. Antioxidant and acetylcholinesterase-inhibitory properties of long-term stored medicinal plants. BMC Compl & Alternat Medicine, 2012, 12:87. Stability of artemisinin in aqueous infusions is also very high and stays stable at least for 24 hours. The same authors also showed that boiling times of 10 minutes extracted more artemisinin than shorter times (op.ci.t). It appears thus reasonable to use concoctions rather than simple infusions. The University of Abomey in Benin also found that the stability of artemisinin in aqueous infusions is excellent. The concentration only decreases by 10% in 20 days. H Zime-Diawara, F Gbaguidi, R Semde, I Some, J Quentin-Leclercq, Effect of cyclodextrins on artemisinin stability and on in vitro dissolution. Stability of lyophilized extracts however is low (Mutaz Akkawi, personal communication). Artemisia annua has a stronger Plasmodium control than the tea reconstituted d from Lyophilized material (Pedro Melillo de Magalhaes, personal communication). A freshly prepared infusion probably contains all the constituents of the plant which have an antimalarial effect. A true polytherapy which explains why the cure rate in all trials in a dozen African countries is >95%. Much higher than for any kind of ACT (artemisinin combined therapy) which are not more than the combination of two monotherapies without synergy but with resistances.