Many anecdotical or scientific results indicate that leaves and stems of Artemisia annua have different therapeutical properties, often higher for leaves, sometimes lower.
Our efforts so far to elucidate key factors explaining these differences have failed. Artemisinin, polyphenols, essential oils are higher in leaves, scopoletin sometimes lower. If the therapeutical properties against malaria, bacteria or nematodes, really are proportional to the concentration of these organic key constituants, the healing power of stems and twigs should be close to zero.
Astonishing is also the fact that Artemisia annua from China sold in European and African pharmacies contains some 80% of stems and twigs
There appears to be one major difference between stems (stalks, twigs-petioles) and leaves : a 2-5x lower concentration of nitrate in leaves than in petioles.
W. Qiu, Z. Wang, Nitrate accumulation in leafy vegetables and its relationship with water. Journal of Soil Science and Plant Nutrition, 2014, 14 (4), 761-168
A pot experiment was carried out, with 30 spinach cultivars to determine nitrate accumulation in leaf blade and petiole. Petiole was the main organ for nitrate accumulation.
Caibian Huang,Zhaohui Wang .Nitrate in leaf and petiole of spinach cultivars. Journal of Plant Nutrition, 2010. 33:8, 1112-1123,
Nitrate content of various parts of a plant differ. Indeed, the vegetable organs can be listed by decreasing nitrate content as follows: petiole > leaf > stem > root > inflorescence > tuber > bulb > fruit > seed. In lettuce and ‘head chicory’, inner leaves accumulate less nitrate than outer leaves and in parsley and spinach, leaf blades accumulate less nitrate than petioles. Nitrate concentration in the petiole was more than double that in the lamina of rocket leaf; the difference was as high as 6.6 times greater in spinach.
Anjana, Shahid UMAR*, Muhammad IQBAL. Nitrate accumulation in plants, factors affecting the process, and human health implications. A review. Agron. Sustain. Dev. 27 (2007) 45–57 45
Santamaria P., Elia A., Serio F., Todaro E. (1999) A survey of nitrate and oxalate content in retail fresh vegetables, J. Sci. Food Agr. 79, 1882–1888.
Medicinal herbs contain on the average higher nitrate amounts than fruits or vegetables : a mean content of 1.240 mg/kg fresh weight versus 336 mg/kg in fruits and vegetables.
Jan Alexander, Diane Benford, Nitrate in vegetables, Scientific Opinion of the Panel on Contaminants in the Food chain1Question N° EFSA-Q-2006-071. The EFSA Journal (2008) 689, 1-79.
The nitrate concentration in plants varies with solar radiation. In spinach leaves it decreases from 1670 mg/kg in the morning to 1390 mg/kg in the afternoon. In the stems it stays constant around 3800 mg/kg during the day. In dried, desiccated herbs or plants these concentrations are multiplied by ten. 100 grams of Artemisia annua tea contain 3 grams of nitrate (30 000 mg/kg).
J Muramoto, Comparison of nitrate content in leafy vegetables from organic and conventional farms in California, Thesis, June 1999, University of California, Santa Cruz.
The cooking process reduces the raw vegetables’ nitrate content from up to 13.40 %, while the frying process increased the vegetables’ nitrate content up to to 29.93%.
Hamzeh Salehzadeh, Afshin Maleki The nitrate content of fresh and cooked vegetables. PLOS, January 9, 2020 https://doi.org/10.1371/journal.pone.0227551
Kurt Steinke, Nitrate accumulation in drought-stressed corn. Michigan State University Extension, Department of Plant, Soil and Microbial Sciences - July 27, 2012
The nitrate-nitrite nitrite oxide pathway has been shown to exist in many alternative herbal medicines or dietary supplements.
The health benefits of nitrates, nitrites and nitric oxide are numerous : cardiovascular, vasodilating, immunity strengthening, bactericidal. The blood lowering effect of potassium is only noticed for KNO³ not for KCl.
They might even contribute to a fascinating property of Artemisia infusions: they protect mild steel against corrosion. It was suggested that artemisinin might be responsible for this property, but it is not very logical as artemisinin is a peroxide
Okafor PC, Ikpi ME, Uwah IE, Ebenso EE, Ekpe UJ, Umoren SA. Inhibitory action of Phyllanthus amarus extracts on the corrosion of mild steel in acidic media. Corrosion Science. 2008;50(8):2310-2317.
The mechanism of this corrosion inhibition has not been elucidated. Some authors relate it to calcium nitrate present in Artemisia plants. Potassium nitrate is used as an anodic inhibitor to prevent corrosion in reinforced concrete structures.
Nitrates and nitrites are produced endogenously in the human body, but 80% come from the diet. Estimation of nitrate and nitrite concentrations of milk sources may provide a better insight. Human milk is known to confer significant nutritional and immunological benefits for the infant. In colostrum (1-3 days postpartum) nitrite concentrations are much higher than in mature milk (0.08 mg/100mL versus 0.001).
The role of NO in malaria therapy is controversial. It’s concentration remains approximately constant during infection. An Australian team investigated the in vitro susceptibility of Plasmodium falciparum to killing by nitric oxide and related molecules. A saturated solution of nitric oxide did not inhibit parasitic growth, but nitrite and nitrate ions were toxic to the parasite in millimolar concentrations.
K A Rockett , M M Awburn In vivo induction of nitrite and nitrate by tumor necrosis factor, lymphotoxin, and interleukin-1: possible roles in malaria. Infect Immun.1992. Sep;60(9):3725-30. doi: 10.1128/IAI.60.9.3725-3730.1992
Nitric oxide is a known mediator of parasite killing by WBC as was shown when the production of NO by arginine is blocked by an inhibitor. Nitric oxide (NO), a highly diffusible cellular mediator involved in a wide range of biological effects, has been indicated as one of the cytotoxic agents released by leukocytes to counteract malaria infection. Human red blood cells infected by Plasmodium falciparum synthesize NO.
Ghigo D, Todde R, Ginsburg H, Costamagna C, Giribaldi G, Deharo E, A. Erythrocyte stages of Plasmodium falciparum exhibit a high nitric oxide synthase (NOS) activity and release an NOS-inducing soluble factor. J Exp Med. 1995 Sep 1;182(3):677-88.
Very important is the inactivation of gametocytes by reactive nitrogen intermediates.
Naotunne TS, Karunaweera ND, Mendis KN, Carter R. Cytokine-mediated inactivation of malarial gametocytes is dependent on the presence of white blood cells and involves reactive nitrogen intermediates. Immunology. 1993;78(4):555-562.
NO may also protect against cerebral malaria.
Cabrales P, Zanini GM, Meays D, Frangos JA, Carvalho LJ. Nitric oxide protection against murine cerebral malaria is associated with improved cerebral microcirculatory physiology. J Infect Dis. 2011 May 15;203(10):1454-63.
The importance of NO in antimalarial immunity has been well documented, especially during sporozoite invasion into hepatocytes. Approximately 5%-10% of the total nitrate intake is converted to nitrite by bacteria in the saliva, stomach, and small intestine.
Kiani, A., Yousefsani, B.S., Doroudian, P. et al. The mechanism of hepatotoxic effects of sodium nitrite on isolated rat hepatocytes. Toxicol. Environ. Health Sci. 9, 244–250 (2017).
A K Nussler , L Rénia, V Pasquetto, F Miltgen, H Matile, D Mazier. In vivo induction of the nitric oxide pathway in hepatocytes after injection with irradiated malaria sporozoites, malaria blood parasites or adjuvants. Eur J Immuno. 1993 Apr;23(4):882-7.
NO is thought to be an important mediator and critical signaling molecule for malaria immunopathology ; it is also a target for therapy and for vaccines.
Nahrevanian H. Immune effector mechanisms of the nitric oxide pathway in malaria: cytotoxicity versus cytoprotection. Braz J Infect Dis. 2006 Aug;10(4):283-92.
NO and related reactive nitrogen intermediates like iNOS can kill and/or inhibit intracellular pathogens such as mycobacteria. NO-donating drugs have therapeutic potential in a number of human diseases including TB.
Yang CS, Yuk JM, Jo EK. The role of nitric oxide in mycobacterial infections. Immune Netw. 2009;9(2):46-52. doi:10.4110/in.2009.9.2.46
Nozaki Y, Hasegawa Y, Ichiyama S, Nakashima I, Shimokata K. Mechanism of nitric oxide-dependent killing of Mycobacterium bovis BCG in human alveolar macrophages. Infect Immun. 1997;65:3644–3647
NO also plays a role in helminthic infections. A Chinese study shows that the key role of NO in blocking the development of Schistosoma japonicum is linked to the inhibition of parasite mitochondrial respiration, which, in turn, leads to decreases in worm survival, egg production and quantity of fertilized eggs.
Jia Shen, De-Hua Lai, R. Alan Wilson, Nitric oxide blocks Schistosoma japonicum. Proceedings of the National Academy of Sciences Sep 2017, 201708578; DOI: 10.1073/pnas.1708578114
Ulrike K. Hahn, Randall C. Bender and Christopher J. Bayne. Involvement of Nitric Oxide in Killing of Schistosoma mansoni Sporocysts by Hemocytes from Resistant Biomphalaria glabrata.The Journal of Parasitology.Vol. 87, No. 4 (Aug., 2001), pp. 778-785
Considering all this, it appears important to include twigs together with the leaves in dried Artemisia herbal tea, but to exclude stalks-stems which are almost worthless.
It is a shame, that research on malaria has neglected nitrates and nitrites, probably because > 90% of the studies have concentrated on the organic extracts of the Artemisia plant, neglecting water soluble molecules, salts and elements.