Τετάρτη, 18 Φεβρουαρίου 2009

Starting Stevia from Seed

Seeds not planted within a few weeks should be stored in a rubber sealed glass jar placed in a cool, dark room or your refrigerator. Sow seeds indoors in early spring, or any time if you have a frost-free climate or plan to keep plants indoors. Transplants should be transferred to the garden at least two weeks after your last frost date. Plants will take at least 8-10 weeks to reach transplant size.
If you have developed a good seed starting method, go ahead and use it. In general, stevia should be treated similar to tomatoes when starting from seed. Here I describe my favorite method. I like to use individual cells or pots such as 6-pack plastic inserts. You will need a plastic flat or shallow container and a clear plastic dome or cover to go on top. Pots or cells should have drainage holes. Standard potting soil or seed starting mix works fine. If the soil is dry, moisten it slightly. Fill cells or pots level without compacting. Place 2-3 seeds on their sides in each cell or pot. Barely cover with fine horticultural vermiculite or a little potting soil.
Moisten thoroughly but gently with a spray bottle to settle the seeds and remove air pockets. Put a little water in the bottom of the flat to be absorbed from the bottom. That should be enough water until plants are up and growing. Place the clear cover on next. It’s fine if it doesn’t fit tightly. A little airflow is good. Put a thermometer under the cover. Place the container under a fluorescent light left on all the time and hung so the height can be adjusted. Keep the air temperature inside the plastic dome between 73˚ F. and 80˚ F. by adjusting the height of the light. A heat mat underneath could do the job as well, but the light itself improves stevia germination slightly.
In 6-12 days, tiny seedlings will begin to emerge. Take the clear cover off when more than half the pots or cells have seedlings showing. Don’t leave it on too long or the humid air will encourage damping off. At this point, leave the light on all the time at about five inches above the plants. Water from below. Pour about ¼ inch of water in the bottom of the flat for the pots or cells to soak up from below. Wait 4-6 days before watering again unless the soil dries out sooner. The goal is to keep the soil slightly moist, but not soggy. Avoid getting the leaves wet.
If the potting soil lacks any compost or fertilizer, Put a few drops of seaweed fertilizer or other weak, low nitrogen fertilizer in the water starting at about the third watering. Plants usually do fine without added fertilizer. When the seedlings are old enough to tell which one in each pot is strongest, cut the others off with a scissors. At about three weeks after sowing, begin to turn the light off at night. Maintain about 14 hours of light per 24-hour period. A timer is nice for this job.
At about 8-10 weeks from sowing, the plants may be transplanted or left to grow a few more weeks. Plants may also be kept as potted plants. A 4-6 inch pot is big enough for a small plant kept trimmed. Bigger pots work even better. Harden plants off for four to six days before transplanting to the garden, placing the plants outside in a protected area on nice days and bringing them in at night.

Pre-Sprouting Method

Transplanting tiny seedlings into their own pots or cells will maximize plant numbers, but this is time consuming and may damage some seedlings. Pre-sprouting is an alternative for maximizing plant numbers. It requires a plastic flat or similar shallow container with a clear plastic dome or lid, a thermometer, a spray bottle, and some biodegradable paper towels. Spread out a single paper towel and moisten with a spray bottle. Spread the seeds across half of the paper towel. Fold the towel in half over the seeds, then in half again. Lay the folded towel in the container along with a thermometer and put on the clear lid. Place under a fluorescent light left on all the time. Adjust the distance from the light so the temperature stays between 75°F. and 80°F. Turn the towel over once a day and spray a little water to keep it moist. In several days when the sprouts have green leaves, cut out a small section of towel where each sprout is located and place each one, green leafy side up, on top of the potting soil in it’s own cell or pot. fill in with a little vermiculite or potting soil so that just the tiny green leaves are showing. Keep moist and the little plants will take root and grow!

Copyright 2006 Jeffrey Goettemoeller

Δευτέρα, 16 Φεβρουαρίου 2009

MEDICINAL PROPERTIES OF Stevia rebaudiana Bertοni

In spite of the prominence Stevia has obtained as a calorie free sweetener and flavour enhancer, it contains a variety of constituents besides the steviosides and rebaudiosides. This including the nutrients specified above and a good deal of sterols, triterpenes, flavonoids, tannins, and an extremely rich volatile oil comprising rich proportions of aromatics, aldehyde, monoterpenes and sesquiterpenes. These and other, as yet unidentified constituents probably have some impact on human physiology and may help explain some of the reported therapeutic uses of Stevia. Stevia has medicinal properties, too. If you use a preparation of the actual plant (not Stevioside), then you may experience benefits other than lowering calories. Scientific research has shown it to be beneficial in regulating blood sugar levels, bringing them into normal range. It is also used as a digestive aid. As a skin care product, it has been used to clear blemishes, tighten skin to remove wrinkles, to heal mouth sores and to treat a variety of wounds. It has also been used to treat eczema, seborrhea and dermatitis.

The following plant chemicals are found in Stevia rebaudiana:

Apigenin-4'-o-beta-d-glucoside, austroinulin, avicularin, beta-sitosterol, caffeic acid, campesterol, caryophyllene, centaureidin, chlorogenic acid, chlorophyll, cosmosiin, cynaroside, daucosterol, diterpene glycosides, dulcosides A-B, foeniculin, formic acid, gibberellic acid, gibberellin, indole-3-acetonitrile, isoquercitrin, isosteviol, jhanol, kaempferol-3-o-rhamnoside, kaurene, lupeol, luteolin-7-o-glucoside, polystachoside, quercetin, quercitrin, rebaudioside A-F, scopoletin, sterebin A-H, steviol, steviolbioside, steviolmonoside, stevioside, stevioside a-3, stigmasterol, umbelliferone, xanthophyll

Hypoglycaemic action:

It is probably the presence of the steviosides themselves that has produced dozens of empirical and semi?controlled reports of hypoglycemic action. Paraguayans say that Stevia is helpful for hypoglycemia and diabetes because it nourishes the pancreas and thereby helps to restore normal pancreatic function in semi?controlled clinical reports one also encounters this action. Oviedo, et.al., reported a 35.2% fall in normal blood sugar levels 6?8 hours following the ingestion of a Stevia leaf extract. Other workers have reported similar trends in humans and experimental animals. These kinds of results have led physicians in Paraguay to prescribe Stevia leaf tea in the treatment of diabetes. Similarly, in Brazil, Stevia tea and Stevia capsules are officially approved for sale for the treatment of diabetes. However, it is important to note that Stevia does not lower blood glucose levels in normal subjects. In one study, rats were fed crude extracts of Stevia leaves for 56 days at a rate of 0.5 to 1.0-gram extract per day. Another team of scientists replicated these procedures.

Neither group observed a hypoglycemic action. Other observers have obtained similar negative results. Then there is research in which the findings show trends toward hypoglycemic action, but are inconclusive. In at least one of these studies, alloxan?diabetic rabbits were used. The authors felt the results supported an anti?diabetic action, but the results were transient at best. To date, the experimental research on the effects of Stevia on blood sugar levels in human patients with either diabetes or hypoglycemia is sparse. The general feeling in the scientific community is that the mild acting nature of the plant and its total lack of toxic side effects argue against the need for extensive and expensive research programs. However, many of the anecdotes reporting a definite and significant blood sugar lowering action in diabetics, and a pronounced exhilarating effect in hypoglycaemic, are sound enough to justify considerable experimental work in the area. Perhaps, when this missing piece to the puzzle is supplied, we will then have a better understanding of how Stevia works. Why, for example, many diabetic humans experience a profound lowering of blood sugar levels following the ingestion of several cups of Stevia tea (24?32 oz.) during the course of a 24-hour period?

Cardiovascular Action:

A good deal of experimental work has been done on the effects of Stevia and stevioside on cardiovascular functioning in man and animals. Some of this work was simply looking for possible toxicity, while some was investigating possible therapeutic action. In neither case have significant properties been found. When any action at all is observed, it is almost always a slight lowering of arterial blood pressure at low and normal doses, changing to a slight rise in arterial pressure at very high doses. The most curious finding is a dose dependent action on heartbeat, with a slight increase appearing at lower doses, changing to a mild decrease at higher doses. In both instance is the result remarkable, and it is extremely doubtful that humans would experience any effect at normal doses. The long-term use of Stevia would probably has a cardiotonic action, that is, would produce a mild strengthening of the heart and vascular system.

Antimicrobial Action:

The ability of Stevia to inhibit the growth and reproduction of bacteria and other infectious organisms is important in at least two respects. First, it may help explain why users of Stevia?enhanced products report a lower incidence of colds and flues, and second, it has fostered the invention of a number of mouthwash and toothpaste products. Research clearly shows that Streptococcus mutans, Pseudomonas aeruginos, Proteus vulgaris and other microbes do not thrive in the presence of the non?nutritive Stevia constituents. This fact, combined with the naturally sweet flavour of the herb, makes it a suitable ingredient for mouthwashes and for toothpastes. The patent literature contains many applications for these kinds of Stevia?based products. Stevia has even been shown to lower the incidence of dental caries.

Digestive Tonic Action:

In the literature of Brazil, Stevia ranks high among the list of plants used for centuries by the "gauchos" of the southern plains to flavour the bitter medicinal preparations used by that nomadic culture. For example, it was widely used in their "mate." Through much experimentation, these people learned that Stevia made a significant contribution to improved digestion, and that it improved overall gastrointestinal function. Likewise, since its introduction in China, Stevia tea, made from either hot or cold water, is used as a low calorie, sweet? tasting tea, as an appetite stimulant, as a digestive aid, as an aid to weight management, and even for staying young.

Effects on the Skin:

One of the properties of a liquid extract of Stevia that has not yet been investigated experimentally is its apparent ability to help clear up skin problems. The Guarani and other people who have become familiar with Stevia report that it is effective when applied to acne, seborrhea, dermatitis, eczema, etc. Placed directly in cuts and wounds, more rapid healing, without scarring, is observed. (This treatment may sting for a few seconds, but a significant lowering of pain follows this). Smoother skin, softer to the touch is claimed to result from the frequent application of Stevia poultices and extracts. Current FDA labelling regulations are forcing U.S. suppliers to label their Stevia as something other than a sweetener; an appeal to its soothing action on the skin has been the most frequent alternative. Stevia is also known for skin shining and tightening properties, and has found its way in several commercial skin tightening products or anti-wrinkle products.


A 1-year, double-blind, placebo-controlled study of 106 individuals with high blood pressure evaluated the potential benefits of stevia for reducing blood pressure.4 In the treated group, the average blood pressure at the beginning of the study was about 166/102. By the end of the study, this had fallen to 153/90, a substantial if not quite adequate improvement. In contrast, no significant reductions were seen in the placebo group.


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Stevioside induces antihyperglycaemic, insulinotropic and glucagonostatic effects in vivo: studies in the diabetic Goto-Kakizaki (GK) rats

Jeppesen PB, Gregersen S, Alstrup KK, Hermansen K.
Department of Endocrinology and Metabolism C, Aarhus University Hospital, Denmark. pbj@mail-telia.dk
Phytomedicine. 2002 Jan;9(1):9-14

Extracts of leaves from the plant Stevia rebaudiana Bertoni have been used in the traditional treatment of diabetes in Paraguay and Brazil. Recently, we demonstrated a direct insulinotropic effect in isolated mouse islets and the clonal beta cell line INS-1 of the glycoside stevioside that is present in large quantity in these leaves. Type 2 diabetes is a chronic metabolic disorder that results from defects in both insulin and glucagon secretion as well as insulin action. In the present study we wanted to unravel if stevioside in vivo exerts an antihyperglycaemic effect in a nonobese animal model of type 2 diabetes. An i.v. glucose tolerance test (IVGT) was carried out with and without stevioside in the type 2 diabetic Goto-Kakizaki (GK) rat, as well as in the normal Wistar rat. Stevioside (0.2 g/kg BW) and D-glucose (2.0 g/kg BW) were administered as i.v. bolus injections in anaesthetized rats. Stevioside significantly suppressed the glucose response to the IVGT in GK rats (incremental area under the curve (IAUC): 648 +/- 50 (stevioside) vs 958 +/- 85 mM x 120 min (control); P < 0.05) and concomitantly increased the insulin response (IAUC: 51116 +/- 10967 (stevioside) vs 21548 +/- 3101 microU x 120 min (control); P < 0.05). Interestingly, the glucagon level was suppressed by stevioside during the IVGT, (total area under the curve (TAUC): 5720 +/- 922 (stevioside) vs 8713 +/- 901 pg/ml x 120 min (control); P < 0.05). In the normal Wistar rat stevioside enhanced insulin levels above basal during the IVGT (IAUC: 79913 +/- 3107 (stevioside) vs 17347 +/- 2882 microU x 120 min (control); P < 0.001), however, without altering the blood glucose response (IAUC: 416 +/- 43 (stevioside) vs 417 +/- 47 mM x 120 min (control)) or the glucagon levels (TAUC: 5493 +/- 527 (stevioside) vs 5033 +/- 264 pg/ml x 120 min (control)). In conclusion, stevioside exerts antihyperglycaemic, insulinotropic, and glucagonostatic actions in the type 2 diabetic GK rat, and may have the potential of becoming a new antidiabetic drug for use in type 2 diabetes.

PMID: 11924770 [PubMed - indexed for MEDLINE]

Analysis of genotoxic potentiality of stevioside by comet assay

Nunes AP, et al.

Departamento de Biofísica e Biometria, Universidade do Estado do Rio de Janeiro, Instituto de Biologia Roberto Alcantara Gomes, Av 28 de Setembro, 87, 20551-030 Rio de Janeiro, RJ, Brazil.

Food Chem Toxicol. 2007 Apr;45(4):662-6. Epub 2006 Oct 27.
Comment in:
Food Chem Toxicol. 2007 Dec;45(12):2597-8; author reply 2599-60
Food Chem Toxicol. 2007 Dec;45(12):2601-2; author reply 2603-4

Stevioside is a natural non-caloric sweetener extracted from Stevia rebaudiana (Bertoni) leaves. It has been widely used in many countries, including Japan, Korea, China, Brazil and Paraguay, either as a substitute for sucrose in beverages and foods or as a household sweetener. The aim of this work was to study its genotoxic potentiality in eukaryotic cells. Wistar rats were treated with stevioside solution (4mg/mL) through oral administration (ad libitum) and the DNA-induced damage was evaluated using the single cell gel electrophoresis (comet assay). The results showed that treatment with stevioside generates lesions in peripheral blood, liver, brain and spleen cells in different levels, the largest effect being in liver. Therefore, these undesired effects must be better understood, once the data present here point to possible stevioside mutagenic properties.

PMID: 17187912 [PubMed - indexed for MEDLINE

Evaluation of the genotoxicity of stevioside and steviol using six in vitro and one in vivo mutagenicity assays

Matsui M et al.
Division of Genetics and Mutagenesis, National Institute of Health Sciences, Tokyo, Japan.
Mutagenesis. 1996 Nov;11(6):573-9.

Stevioside, a constituent of Stevia rebaudiana, is commonly used as a non-caloric sugar substitute in Japan. The genetic toxicities of stevioside and its aglycone, steviol, were examined with seven mutagenicity tests using bacteria (reverse mutation assay, forward mutation assay, umu test and rec assay), cultured mammalian cells (chromosomal aberration test and gene mutation assay) and mice (micronucleus test). Stevioside was not mutagenic in any of the assays examined. The aglycone, steviol, however, produced dose-related positive responses in some mutagenicity tests, i.e. the forward mutation assay using Salmonella typhimurium TM677, the chromosomal aberration test using Chinese hamster lung fibroblast cell line (CHL) and the gene mutation assay using CHL. Metabolic activation systems containing 9000 g supernatant fraction (S9) of liver homogenates prepared from polychlorinated biphenyl or phenobarbital plus 5,6-benzoflavone-pretreated rats were required for mutagenesis and clastogenesis. Steviol was weakly positive in the umu test using S.typhimurium TA1535/pSK1002 either with or without the metabolic activation system. Steviol, even in the presence of the S9 activation system, was negative in other assays, i.e. the reverse mutation assays using S.typhimurium TA97, TA98, TA100, TA102, TA104, TA1535, TA1537 and Escherichia coli WP2 uvrA/pKM101 and the rec-assay using Bacillus subtilis. Steviol was negative in the mouse micronucleus test. The genotoxic risk of steviol to humans is discussed.
PMID: 8962427 [PubMed - indexed for MEDLINE

Mutagenicity and human chromosomal effect of stevioside, a sweetener from Stevia rebaudiana Bertoni

Suttajit M, Vinitketkaumnuen U,Meevatee U, Buddhasukh D
Department of Biochemistry, Chiang Mai University, Thailand.
Environ Health Perspect.1993 Oct;101 Suppl 3:53-6.

Leaves of Stevia rebaudiana Bertoni have been popularly used as a sweetener in foods and beverages for diabetics and obese people due to their potent sweetener stevioside. In this report, stevioside and steviol were tested for mutagenicity in Salmonella typhimurium strains TA98 and TA100 and for chromosomal effects on cultured human lymphocytes. Stevioside was not mutagenic at concentrations up to 25 mg/plate, but showed direct mutagenicity to only TA98 at 50 mg/plate. However, steviol did not exhibit mutagenicity in either TA98 or TA100, with or without metabolic activation. No significant chromosomal effect of stevioside and steviol was observed in cultured blood lymphocytes from healthy donors (n = 5). This study indicates that stevioside and steviol are neither mutagenic nor clastogenic in vitro at the limited doses; however, in vivo genotoxic tests and long-term effects of stevioside and steviol are yet to be investigated.

PMID: 8143647 [PubMed - indexed for MEDLINE]

Study of physiological and toxic effects of a sweetening agent stevioside (review of the literature)

Smirnova MG
Vopr Pitan. 2001;70(4):41-4.

The review consist of modern data of physiologic and toxic effects on organism of sweetening stevioside with low energy value. His sweetening is considered by the most of investigators as not toxic, not mutagenic and not cardinogenic one.

PMID: 11550460 [PubMed - indexed for MEDLINE