Indian almond leaves contain various tannins, including punicalagins, as well as several different flavonoids, such as kaempferol and quercetin. Also, when Indian almond leaves are subjected to microbial degradation in water humic substances are formed.
What are tannins?
Tannins are astringent, bitter plant polyphenols. The destruction or modification of tannins plays an important role when fruit ripens and wine matures, and the presence of tannins are why unripe fruit and certain types of wine can make your mouth feel dry and cause your lips to pucker 1.
Tannins are widely distributed in many species of plants, where they protect the plants from predation. Tannins are also suspected of playing a role in plant growth regulation. Tannins are typically found in the surface wax or in the vacuoles of plants, where they won’t affect plant metabolism as long as the plant tissue is alive. When a leaf or other plant part dies, the cell breakdown will cause the tannins to be active in metabolic effects. In addition to this, tannins present in the heartwood of conifers are believed to be partly responsible for the natural durability of the wood by inhibiting microbial activity.2
When large amounts of tannin rich plant material end up in a slow flowing river, they create a type of habitat commonly referred to as blackwater. You can read more about tannins and blackwater rivers below.
What are punicalagins?
Punicalagins are large polyphenols compounds found in various plants, especially in pomegranades, indian almond leaves, the shrubs Cistus salvifolius and Combretum molle, and in a few species belonging to the genera Myriocarpa. Punicalagins are water soluble and have high bioavailability.
Punicalagins acts as antioxidants and are the major component responsible for the antioxidant health benefits of pomegranates. Punicalagins caught the attention of cancer researchers after a Taiwanese study8 showed that punicalagin alpha (1-alpha-O-galloylpunicalagin) inhibited certain types of intracellular signalling molecules (extracellular signal-regulated kinases, c-Jun N-terminal kinases and protein kinases to be exact) that play roles in cancer growth.
Tannins and Blackwater rivers
Tannins are what give Blackwater rivers their characteristic tea-colour appearance and low pH-value.
Blackwater rivers flows slowly through forested environments, e.g. swamps and wetlands, with ample amounts of vegetation. As the vegetation decays in the water, the tannins are leached out, resulting in transparent but darkly stained acidic water. The famous Rio Negro on the South American continent is for instance known to have a pH-value of 4.5-5.7. Compared to whitewater rivers, blackwater rivers are nutrient poor and have ionic concentrations only slightly higher than rainwater. The aluminium concentration is much greater in blackwater (because of the acidity), while the amounts of sodium, magnesium, potassium and calcium are much lower. The scarcity of dissolved ions in blackwater results in a conductivity that is almost as low as that of rainwater.
The unique characteristics of the blackwater river have lead to the formation of a flora and fauna that differs significantly from what you would find in other types of rivers. It is for instance difficult for snails to live in blackwater since they need calcium to build their shells.
What are flavonoids?
Flavonoids are a class of plant secondary metabolites widely distributed in plants where they fulfil various functions. Flavonoids will for instance protect plants from microbes and insects, and they also make up the most important pigment in yellow and red flower petals. Flavonoids are famous for their antioxidant activity and the beneficial effects of tea and red wine on the human body have been attributed to flavonoids [9 ][10 ].
Certain flavonoids are believed to decrease the risk of developing some types of cancer, but the field is far from thoroughly researched yet and more studies will be needed before anyone can know for sure how flavonoids affect the human body. According to a cancer study carried out at the University of California, Los Angeles (UCLA), eating certain flavonoids seemed to decrease the risk of developing lung cancer. Dr. Zuo-Feng Zhang, of the UCLA’s Jonsson Cancer Center and a professor of public health and epidemiology at the UCLA School of Public Health, said the flavonoids that appeared to be the most protective included catechin, kaempferol and quercetin11 . There is also an 8-year study in which kaempferol, quercetin and another flavonoid named myricetin reduced the risk of pancreatic cancer by 23 percent.12
What is kaempferol?
Kaempferol is a natural flavonoid found in certain plants. We do for instance ingest kaempferol when we eat brussel sprouts, broccoli, apples, and grapefruit. As mentioned above, kaempferol has been linked to a decreased risk of developing certain types of cancer.
What is quercetin?
Just like kaempferol, quercetin is a flavonoid present in some plants. Capers, lovage, apples, tea and red onions are all examples of products rich in quercetin. Kaempferol is currently being investigated for a wide range of potential health benefits, including anti-inflammatory and antioxidant properties13 .
What are humic substances and humic acid?
Humic acid is one of the major components of humic substances. When organisms such as plants are broken down by bacteria and fungi, the result is humic substances – the dark brown material that you find in the type of soil commonly referred to as humus.
3: Akiyama H, Fujii K, Yamasaki O, Oono T, Iwatsuki K (October 2001). “Antibacterial action of several tannins against Staphylococcus aureus“. J. Antimicrob. Chemother. 48 (4): 487–91. doi:10.1093/jac/48.4.487. PMID 11581226
4: Funatogawa K, Hayashi S, Shimomura H, et al. (2004). “Antibacterial activity of hydrolyzable tannins derived from medicinal plants against Helicobacter pylori“. Microbiol. Immunol. 48 (4): 251–61. PMID 15107535
5: Cheng HY, Lin CC, Lin TC (September 2002). “Antiherpes simplex virus type 2 activity of casuarinin from the bark of Terminalia arjuna Linn”. Antiviral Res. 55 (3): 447–55. doi:10.1016/S0166-3542(02)00077-3. PMID 12206882
7: Kolodziej H, Kiderlen AF (September 2005). “Antileishmanial activity and immune modulatory effects of tannins and related compounds on Leishmania parasitised RAW 264.7 cells“. Phytochemistry 66 (17): 2056–71. doi:10.1016/j.phytochem.2005.01.011. PMID 16153409
8: Chen LG, Liu YC, Hsieh CW, Liao BC, Wung BS. “Tannin 1-alpha-O-galloylpunicalagin induces the calcium-dependent activation of endothelial nitric-oxide synthase via the phosphatidylinositol 3-kinase/Akt pathway in endothelial cells.” PMID: 18435486
10: Hirofumi Tachibana, Kiyoshi Koga, Yoshinori Fujimura & Koji Yamada; “A receptor for green tea polyphenol EGCG”. Nature Structural and Molecular Biology, 2004, http://dx.doi.org/doi:10.1038/nsmb743
11: Baek Nam-In; Kennelly E.J.; Kardono L.B.S.; Tsauri S.; Padmawinata K.; Soejarto D.D.; Kinghorn A.D., “Flavonoids and a proanthrocyanidin from rhizomes of Selliguea feei”. Phytochemistry, 1994, vol. 36, no2, pp. 513-518 (19 ref.)