Peppermint (Mentha piperita)

Posted on December 13, 2024 by Robert Barrington

Peppermint (Mentha piperita) is a widely consumed herbal tea that may have beneficial health effects. Peppermint tea is usually made from peppermint leaves that have a distinctive armour because of the phytochemicals they contain. These phytochemicals include an essential oil that is largely responsible for the taste and smell of peppermint because of its volatile component. The leaves are rich in antioxidants that include rosmarinic acid and high levels of the flavonoids eriocitrin, luteolin and hesperidin are also present. Topically peppermint has antimicrobial properties, but these are not evident upon consumption. One of the main physiological activities of peppermint, that likely results from the essential oils, is a significant relaxing effect on the gastrointestinal wall. Peppermint can also cause an analgesic and anaesthetic effect on the peripheral nervous system, as well as immunomodulating effects. These effects make peppermint an effective strategy to treat certain gastrointestinal tract problems such as stomach cramps and irritable bowel syndrome. 

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McKay, D. L. and Blumberg, J. B. 2006. A review of the bioactivity and potential health benefits of peppermint tea (Mentha piperita L.). Phytotherapy Research: An International Journal Devoted to Pharmacological and Toxicological Evaluation of Natural Product Derivatives. 20(8): 619-633

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Centella asiatica (Gotu Kola): Phytochemistry

Posted on December 12, 2024 by Robert Barrington

Centella asiatica is a plant commonly known as gotu kola. The plant grows in large areas of the tropical and subtropical regions of the world, and its harvesting is important as it has a long tradition of medicinal uses. The phytochemicals within gotu kola include terpenoids such as asiatic acid, madecassic acid, asiaticoside, madecassoside, brahmoside, brahmic acid, brahminoside, thankiniside, isothankunisode, centelloside, madasiatic acid, centic acid, and cenellic acid. These chemicals are thought to provide the consumer of the plant with health benefits that include a significant reduction in the negative effects of stress. The plant also contains polyphenols, particularly the flavonoids  quercetin, kaempferol, catechin, rutin, apigenin and naringin which may explain the antioxidant activity of the herb. Vitamins in the herb include vitamin C, thiamine, riboflavin, niacin, carotenoids and vitamin A. The plant possesses a volatile oil which contains chemicals including caryophyllene, farnesol and elemene. 

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Seevaratnam, V., Banumathi, P., Premalatha, M. R., Sundaram, S. P. and Arumugam, T. 2012. Functional properties of Centella asiatica (L.): a review. International Journal of Pharmacy and Pharmaceutical Sciences. 4(5): 8-14

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Lymph Chylomicrons

Posted on December 11, 2024 by Robert Barrington

Chylomicrons are a physiological phenomenon that form as a result of triglyceride absorption. Chylomicrons are high in triglycerides and are particles that can be considered as a class of lipoprotein. Chylomicrons can be seen in the blood following absorption of fat from the intestine and have been isolated from the lymph. The size of the chylomicrons located in the lymph and blood are related to the amount of triglycerides in the intestine and the speed of its absorption, and this is in turn determined by the amount of fat in the diet. The phospholipids that comprise the chylomicron particles are mainly lecithin with smaller amounts of sphingomyelin and phosphatidylethanolamine. The fatty acids present in chylomicrons may differ from the fatty acids in the diet because metabolism of the fatty acids occurs in the intestinal mucosa. The chylomicrons have a lipid core made up of fatty acids and cholesterol, and surrounding this is a surface membrane made up of phospholipids and proteins. The function of chylomicrons is to transport fatty acids and cholesterol from the intestine to the liver for repackaging and metabolism. 

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Green, P. H. and Glickman, R. M. 1981. Intestinal lipoprotein metabolism. Journal of Lipid Research. 22(8): 1153-1173

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The Tocopherol Transfer Protein

Posted on December 10, 2024 by Robert Barrington

Vitamin E is a group of 8 isomers that share a biological activity with the main form alpha tocopherol. Vitamin E is an important antioxidant in humans and animals, where its primary role is to protect the cell membranes from lipid peroxidation. Plasma vitamin E levels are determined by the ability of the body to absorb the vitamin from the gut, and to transfer the absorbed vitamin E to the liver, where it is packaged into lipoproteins for distribution to the tissues. The rate limiting step in this process is the transfer of the vitamin E from the gut to the liver, and this is a step that involves the tocopherol transfer protein. The tocopherol transfer protein has various affinities for the 8 isomers of vitamin E, but its highest affinity is for alpha tocopherol. Along with the fact that alpha tocopherol is the most predominant form of the vitamin in the diet, this explains why in humans alpha tocopherol is the dominant form of the vitamin in tissues. Relative affinities for isomers of vitamin E compared to alpha tocopherol are 38 % for beta tocopherol, 9 % for gamma tocopherol and 2 % for delta tocopherol. Alpha tocopheryl acetate had a relative affinity of 2 %, whereas alpha tocotrienol had a relative affinity of 12 %. This shows that the tocopherol transfer protein has a preference for alpha tocopherol in humans and this is a critical determinant of biological activity. 

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Hosomi, A., Arita, M., Sato, Y., Kiyose, C., Ueda, T., Igarashi, O., Hiroyuki, A. and Inoue, K. (1997). Affinity for α‐tocopherol transfer protein as a determinant of the biological activities of vitamin E analogs. FEBS letters. 409(1): 105-108

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Quercetin and Blood Pressure

Posted on December 9, 2024 by Robert Barrington

Quercetin is a flavonoid belonging to the flavanol sub-group. It is found in plants bound to various sugar moieties and its absorption in humans has been evidenced, particularly from onions. Quercetin may have a number of health effects in humans and its role in human health has been investigated. For example, in one study researchers administered 730 mg of quercetin per day for 29 days to hyper tensive subjects in the form of a quercetin supplement. The results of the study showed that reductions in systolic, diastolic and mean arterial pressures were experienced by those patients who fitted into the classification of stage 1 hypertension. These results show that supplemental quercetin may be able to lower blood pressure in those with elevated levels. This study did measure the oxidative stress of the individuals but found no change with quercetin supplementation. This may suggest that the mechanism of action could be independent of the antioxidant activity of quercetin, or that the equipment was not sensitive enough to measure any changes. It also suggests that supplemental quercetin can have beneficial effects, which is an important consideration as supplements tend to be in the aglycone form of quercetin, compared to glycosides in plants. 

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Edwards, R. L., Lyon, T., Litwin, S. E., Rabovsky, A., Symons, J. D. and Jalili, T. 2017. Quercetin Reduces Blood Pressure in Hypertensive Subjects. The Journal of Nutrition. 137: 2405–2411

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Food Sources of Niacin

Posted on December 6, 2024 by Robert Barrington

Grains, nuts, legumes and meat are food sources of niacin. Of these, the plant sources, which are grains, nuts and legumes, only have modest amounts of niacin. In contrast, meat can have higher amounts of niacin and may release 2 to 5 mg of niacin per average portion in the form of NAD stored in cells within the tissues. In addition, foods that contain tryptophan can improve the niacin status of the individual because the tryptophan is converted to NAD in the liver. These sources are all natural sources of niacin, but niacin is also sometimes added to cereals and flour, and this can provide a significant dietary source. Generally the presence of niacin, added to flour and cereals has reduced the risk of pellagra in developed countries, although pellagra is still found in alcoholics and those with eating disorders such as anorexia nervosa. The average daily intake of niacin in the United States has been estimated to be 32 mg in 2004, an increase from 16 mg in 1930, largely because of fortification of food. Despite the lack of pellagra in developed countries, subclinical deficiencies are still widespread. These may manifest as conditions such as depression and nervous disorders. Polymorphisms are more common for niacin requiring enzymes than many other vitamins as there are so many niacin requiring enzymes in the human metabolic pool. This increases the complexity of understanding niacin requirements in human populations considerably. 

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Prousky, J., Millman, C. G. and Kirkland, J. B. 2011. Pharmacologic use of niacin. Journal of Evidence-Based Complementary & Alternative Medicine. 16(2): 91-101

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Niacin Metabolism

Posted on December 5, 2024 by Robert Barrington

Niacin, sometimes called vitamin B3, is present in the human diet in a number of forms. Nicotinic acid is technically a precursor form found in plants that can be converted to nicotinamide adenine dinucleotide (NAD) in the liver. This NAD is subsequently used in redox reactions in tissues. The NAD pool is maintained in tissues in the oxidised state, but can be readily reduced as part of the energy producing pathways. Animal forms of niacin can be consumed directly as NAD as this is present in the animal’s tissues, and this can be metabolised in the liver to form niacinamide and release to the blood. Dietary nicotinic acid is converted to NAD in the small intestine and liver. Subsequently this can be metabolised in the liver to form niacinamide. Niacinamide formed in the liver can be released into the blood. The amino acid tryptophan can also be converted in the liver to NAD, but this conversion rate is low in humans. Because nicotinic acid (the plant precursor) is converted to NAD in the liver and then released into the blood as niacinamide, little nicotinic acid appears in the blood. However, high dose supplements can overload this conversion process and result in higher levels of nicotinic acid in the blood.

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RdB

Prousky, J., Millman, C. G. and Kirkland, J. B. 2011. Pharmacologic use of niacin. Journal of Evidence-Based Complementary & Alternative Medicine. 16(2): 91-101

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Niacin and Sexual Function

Posted on December 4, 2024 by Robert Barrington

Niacin is sometimes called vitamin “B3” as it is categorised within the B vitamin group of essential organic compounds. Niacin is generally regarded as an essential compound although it can be synthesised in small amounts from L-tryptophan in the liver. High intakes of niacin have been shown to normalise blood lipid levels in those with a dysfunction. One of the effects of high doses of supplemental niacin is an increase in blood flow which can cause peripheral tissue to experience increased blood flow due to dilation of capillaries via altered prostaglandin metabolism. This may explain the benefits for niacin in cases of erectile dysfunction in the short term. However, the effects of niacin of erectile dysfunction may be most evident in those with an underlying dyslipidaemia. This suggests that the two factors, erectile dysfunction and dyslipidaemia may be linked. However, to achieve this the doses in some studies have been very high, and in one study were 1500 mg per day of niacin for 12 weeks. 

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RdB

Ng, C. F., Lee, C. P., Ho, A. L. and Lee, V. W. 2011. Effect of niacin on erectile function in men suffering erectile dysfunction and dyslipidemia. The Journal of Sexual Medicine. 8(10): 2883-2893

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Withanolides: Health Effects

Posted on December 3, 2024 by Robert Barrington

Withanolides are a group of C28 steroidal chemicals first found in the herb Withania somnifera and later in other plants. In Withania somnifera, the main withanolides that are active in humans and animals biologically are withanolide A and withanolide D. Withanolides serve important functions in Solanaceous plants including the ability to repel insects. However, in humans and animals they have a wider range of physiological functions including anti-cancer, antioxidant, antimicrobial, adaptogenic, immunomodulating, hepatoprotective, antistress, anti-inflammatory, radiosensitising and antiarthritic effects. Each withanolide has a slightly different effect based on the substitution patterns on the structure. The withanolide explains some, but not all, of the biological effects from consumption of Withania somnifera, and in particular may explain the adaptogenic properties of the herb. In this regard, withanolides are analogous behaviourally to ginsenosides in Panax ginseng which are well reported to have adaptogenic properties in humans and animals. 

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Budhiraja, R. D., Krishan, P. and Sudhir, S. 2000. Biological activity of withanolides. Journal of Scientific and Industrial Research. 50: 904-911

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Withania somnifera: Phytochemistry

Posted on December 2, 2024 by Robert Barrington

Withania somnifera is a plant that is also called ashwagandha. This herb is used in traditional medicine to treat a number of health complaints, and the health benefits it confers is as a direct result of the phytochemicals it contains. Studies have assessed the phytochemistry of withania, and in particular have studied the roots of the plant that are used medicinally. These studies reveal the presence of around 35 chemical constituents that may be responsible in whole or in part for the various health effects of the plant. It is thought that the main active constituent in the plant’s roots are a group of alkaloids including isopellertierine, anahygrine, cuscohygrine, pseudotropine, somniferinine, somniferiene, tropanol, withanine, withananine and anferine; steroidal lactones including withanolides and withaferins; saponins with an acyl functional group including sitoindoside VII and VIII; as well as withanolide glucosides including sitonidoside XI and X. The steroidal structure of withanolides is similar to the main active constituents in Panax ginseng, the latter containing steroidal molecules called ginsenosides. The main withanolides present in withania include withaferin A and withanolide D. Withanolides are likely adaptogenic compounds and may reduce the effects of stress hormones in humans and animals. Withania is also high in iron, and this may provide some of the anti-fatigue effects of the herb. 

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Singh, G., Sharma, P. K., Dudhe, R. and Singh, S. 2010. Biological activities of Withania somnifera. Annals of Biological Research. 1(3): 56-63

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