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 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.
There appears to be one major difference betweeen stems (stalks, twigs, petioles) and leaves : a 2-3x lower concentration of nitrate in leaves Nitrate assimilation in plants mainly occurs in leaves by nitrate reductase activity (NRA), and more even in young leaves. Leaves show NRA levels two to three times higher than stems (BL Black et al., Tree Pysiology, 22, 717-724, 2002). Medicinal herbs contain on the avarage higher amounts than fruits or vegetables : a mean nitrate concentration of 1.240 mg/kg fresh weight versus 336 mg/kg in fruits and vegetables (EFSA Journal, 2008, 689, 1-79).The nitrate-nitrite.nitrite oxide pathway has been shown to exist in many alternative herbal medicines or dietary supplements. 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 (J Muramoto, University of California, Santa Cruz, 1999)
The plant Artemisia is an accumulator for many minerals : potassium, selenium, nitrate, iron (A Traore, M Diallo…P Lutgen. Afric J Biotechnol 12-26, 4179-86, 2013). Artemisia thrives on nitrate rich soils 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).
The health benefits of nitrates, nitrites and nitric oxide are numerous: cardiovascular, vasodilating, immunity strengthening, bactericidal. The blood pressure lowering effect of potassium is only noticed for KNO³ not for KCl (V Kapil, A Milsom et al., Hypertension, 2010). Dietary nitrate has recently emerged as a potential modulator of muscle energy metabolism and a possible « natural » ergogenic aid to exercice performance ( K Landsley et al., Medicine and Science in Sports and Exercice, 2011, 1125-1131). It is now fully recognized that health hazards of nitrates and nitrites have been overestimated. No study could confirm the risk of cancer or methemoglobina for normal dietary intakes.
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). Nitrate concentrations are low at the beginning but steadily increasing. According to the authors (N Hord et al., Breastfeeding Medicine, 6-6, 2011, 393-399) this change is partly due to the changing intestinal microflora in the baby and the changing metabolic demands as the baby grows. The beneficial effects of NO in adult stomachs on gastroprotective and immunomodulatory functions is known. Arginine plays a key role in the metabolism of nitrates. Therefore it is reasonable to surmise that nitrite must be supplied to the newborn by colostrum. A recent thesis from Sweden (C Jädert, Karolinska Institutet, 2014) confirms and documents well all these positive elements. Dietary nitrates have potent anti-inflammatory effects, without impairing the ability to clear an infection. They are able to restore the gastric and colonic mucus layer in case of colitis.
The role of NO in malaria therapy however 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 (KA Rockett et al., Infection and Immunity, 1991, 3280-3283).