Pecan Nut Shell Extract

This post looks briefly at three Brazilian publicans on the dietary use of aqueous extracts of pecan nut shells, or pecan nut shell “tea.”   A U.S. publication on “pecan shell flour” is also presented.   The first paper suggests that pecan shell tea might actually help with the symptoms of nicotine withdrawal.  The second Brazilian paper tests the toxicity of pecan shell tea.  A US paper establishes the safety of a pecan flour in a rat model.  A list of organic compounds found in aqueous and ethanol/aqueous extracts is also presented.

Pecan shell tea protection from cigarette smoke induced brain lipid oxidation

In 2011 Reckziegel and other Brazilian coworkers addressed the hypothesis that an anti-oxidant enriched pecan shell tea could reduce the oxidative stress associated with cigarette smoke withdrawal in mice.  Other rat withdrawal anxiety symptoms were examined.

• 10 controls. Mice were given only tap water to drink and were not exposed to cigarette smoke.
• 10 smokers.  Mice were placed in a chamber in which a local brand of cigarettes were burned at a rate of 6, 10, and 14  daily during the first, second, and third weeks, respectively).
• 10 Pecan tea drinkers.  Mice were given pecan shell tea prepared with 25g per liter water instead of tap water. 10 smokers and tea drinkers
• 10 smokers also drinking pecan tea

Fifteen hours after smoking cessation, mice were subjected to psychological stress tests.  After completing these tests, red blood cells and brains were removed and assayed for markers of lipid peroxidation.

The authors were basically detecting the lipid peroxidation product MDA by reacting it with thiobarbituric acid and measuring the appearance of a colored reactant product.  The authors also showed weak  correlation between stress behaviors and the level of MDA in the red blood cells.  The aqueous extract (AE) of pecan shells also preserved ascorbic acid levels as well as catalase activity.  Catalase is an enzyme that detoxifies hydrogen peroxide.

Pecan shell safety

As a side note, heavy metals may present a problem

Porto and coworkers (2016) determined that organic and inorganic compounds from an aqueous extract of pecan shells had a lethal dose to 50% of the tested male mice,  LD₅₀ , of 1.166.3 g kg⁻¹ .  Inorganic salts were assayed in this study.   High levels of Cu and Mn, (29.9 ± 14.5 ppm and 128.3 ± 7.3 ppm) were reported as cause for concern.  The oxidation state of Cr, present at 4.5 ± 0.2 ppm, was not given.

If pecan shells are not contaminated with heavy metals and other toxins, they are safe?

The South Georgia Pecan Company and the Southeastern Reduction enlisted the help of the Burdock Group to get  pecan flour listed as generally recognized as safe (GRAS) by the US FDA.  The toxicology assessment (Dolan 2016) was only part of the process. Other information supplied by South Georgia Pecan and its subsidiary Southeastern Reduction show that pecan shell flour has at least as much antioxidant capacity as common berries.

In the Burdock Group study male and female rats were given 0, 50, 100, and 150 g/kg of pecan shell flour per day.  In the Burdock group study target exposures for a rat consuming 25g feed per day

• 0g, control
• 3.571g or 50 g per kg feed
• 7.143g or 100 g per kg feed
• 10.714g  or 150 g per kg feed

The test diets were prepared weekly by thoroughly blending the test substance into the basal diet with a high-speed mixer. All prepared test and control diets were stored under refrigeration until use.  Gallic acid, see pecan shell component section, was used as a means of testing the stability of pecan flour components in the rat feed matrix.

Functional observational tests

During Week 12 of the study each animal was evaluated for neurological functions.  Motor activity was monitored using an automated Photobeam Activity System®

A PAS seems to be s specialized box with a pressure sensitive floor that evaluates motor activity as well as the psychological response to a strange environment.

• excitability in open field
• gait and sensori-motor coordination in open field.
• manipulative evaluations
• autonomic function
• reactivity and sensitivity, elicited behavior
•  convulsions, tremors, unusual, or bizarre behavior
• emaciation, dehydration and general appearance
• forelimb and hind limb grip strength
• foot splay measurements

No signs of neurological toxicity were reported.  Like the Reckziegel (2011) report ameliorating effects of tobacco smoke withdrawal, much of the evaluation seems to be based on the investigators’ familiarity of rat behavior that may be difficult to communicate in writing.

Weight gain

During the course of this 90 day feeding study the weight of male rats increased about three fold.  Female rats merely doubled in weight.   Pecan shell flour did not slow or increase weight gain in either gender with the exception of females on the 100 g per kg feed.  Their weight increased slightly more.

The amount of feed eaten was also monitored.  The amount of pecan shell flour in the females’ food had no bearing on their consumption.  The males on the 150 g per kg feed ate slightly more over the 91 day period.  There were a few weeks towards the end of the study in which the male rats on the 100 g per kg feed ate more than the controls.   Feed efficiency decreased in males receiving 150 g per kg feed on Days 0–7, 21–28, and overall (Days 0–91) (p < 0.01).

Many humans wishing to lose weight would love to see “feeding efficiency” go down.  A chicken farmer may want to increase the weight of the chickens as much as possible with the least amount of feed.  What was not considered in this preliminary report was the influence of non digestible carbohydrates on the intestinal micobiota of the animals.

Blood work

Red blood cell attributes from size to hemoglobin concentration are used as a measure of toxicity.  The mean cell hemoglobin (MCH) was slightly, and statistically significantly, lower than the control for the male rats in the 150 g per kg group.  The lower MCH was in reference values for this strain of rat such that the difference was not functionally significant. A slight increase in basophils was in females on the high dose.  Because this value was in a rather large reference range, and in absence in changes of other white cell counts, this increase was deemed functionally insignificant.

Liver function

Changes in liver enzymes in the blood were not detected in any pecan flour treatment group, male or female.  Bilirubin was observed to increase in the 150 g per kg male feed group. Cholesterol was observed to increase in the 150 g per kg female feed group.  These changes were regarded as within reference values and functionally not consequential.  Triglycerides were decreased in the mid dose female group.  The triglycerides for all pecan flour fed females were reduced by 22-29%, even if not statistically different from the control.

Organ weights at the end of 91 Days

The organs of the rats were removed, weighed, and examined for damage or disease.  The only statistical difference was seen in the male rats in the highest feed group of 150g kg pecan shell flour.  In these cases the spleen and liver weights as a fraction of total body weight were slightly decreased.  These ratios were within the historical range of controls for this strain of rat.  Other tissue abnormalities were noted in the Toxicology Reviews publication were dismissed as being sporadic and not due to the treatment.

Gene mutations and chromosomal damage

The Reverse Mutation/Ames Test

The Ames test utilizes strains of Salmonella that are unable to make their own histidine because of mutations in the genes that code for histidine synthesis enzymes..  They can grow just fine as long as the medium contains histidine.  TA98 contains a frame shift mutation in hisD caused by deletion of say two of the three base pairs in the codon.    Deletion of a third base pair brings the reading of codons back into frame. TA100 contains a lethal base pair substitution in the hisD gene.  TA1537 is another strain used to detect frame shifts due to base pair deletion.  TA1535 is also used to detect point mutations.   A liver microsome enzyme S9 mix is often added to test the hypothesis that liver enzymes are required to transform the test compound into a mutagen.

• Pecan shell flour in plate
• Bacteria preincubated in pecan shell flour

While precipitates were formed at higher concentrations, eg >1mg per plate, reverse mutations above background were never observed, with or without liver S9 activation.

Micronuclei

Micronuclei are regarded as signs of genotoxicty or chromosomal instability that result in incorrect segregation of chromosomes in the daughter cells of a cell that has undergone division.    In the micronucleus test, groups of mice (n = 5/gender) were dosed
with 3333 mg/kg body weight.  The negative control was the cottonseed oil vehicle.  The positive control was cyclophosphamide.  Samples of blood were taken from the
tail vein at 44 h (all groups) and 68 h after the last dose.  While the pecan shell flour resulted in a slight and statistically significant44 hour  increase in micronuclei in males and females, the increase was considered functionally insignificant because the micronuclei were within the historical range of negative controls and much less than the positive controls.

A foot note…

Southeastern Rendering also paid the Brunswick company to compare the reactive oxygen and nitrogen scavenging activity of pecan flour with freeze dried blueberries,  strawberries, cranberries,and raspberries.  Hydroxyl and peroxyl radicals were evaluated as were the peroxynitrate and superoxide anions and singlet oxygen.  In a way these results are extremely encouraging considering the high copper concentrations observed by Porto and coworkers.  Copper and ascorbate, aka viatamin C, can redox cycle to generate hydroxyl radicals in a process called the Fenton reaction.   Ascorbate  can act as a pro-oxidant as well as an anti-oxidant.

What is in pecan shells?

The following is a list from Billig and coworkers (2018) of phenolic compounds extracted from pecan nut shells using  20% v/v of ethanol/water at  60 and 80 °C.  Most of the components are found in foods.  The following list was obtained from the abstract.  Information was obtained from PubChem, Wikipedia, and PubMed.

vanillin and related compounds

Vanillin (PubChem CID: 1183) is the primary extract of the vanilla bean.

Vanillic acid (PubChem CID: 8468) is a flavoring agent and the oxidized form of vanillin.

Salicylic acid (PubChem CID: 338)  is a compound obtained from the bark of the white willow and wintergreen leaves. It has bacteriostatic, fungicidal, and keratolytic actions.   It has direct activity as an anti-inflammatory agent and is a precursor to acetylsalicylic acid, aspirin.

Mandelic acid (PubChem CID: 1292) is an aromatic alpha hydroxy acid used in the treatment of urinary tract infections and as an oral antibiotic.  A Pakistani group has recently reported on isolation of mandelic acid from the Indian horse chestnut  PubMed.

Gallic acid (PubChem CID: 370) is a flavoring agent that is found free or as part of tannins.  Gallic acid is found in gallnuts, sumac, witch hazel, tea leaves, oak bark, and other plants.  It is commonly used in the pharmaceutical industry.

Siryngic acid (PubChem CID: 10742) is found in some distilled alcoholic beverages.  Research suggests that phenolics from wine may play a positive role against oxidation of low-density lipoprotein (LDL), which is a key step in the development of atherosclerosis. Syringic acid is correlated with high antioxidant activity and inhibition of LDL oxidation.

Protocatechuic acid (PubChem CID: 72) Protocatechuic acid (3, 4-dihydroxybenzoic acid) is a natural phenolic compound found in many edible and medicinal plants.  Green tea is one example of both. Recent studies indicate that it could be used as a protective agent against cardiovascular diseases and neoplasms. The mechanism of its action is mostly associated with antioxidant activity, including inhibition of generation as well as scavenging of free radicals and up-regulating enzymes which participate in their neutralization.

P-anisic acid (PubChem CID: 7478)  is a phenolic acid, an organic molecule commonly found in anis-seed, a common food spice. Anisic acid is occasionally found in human biofluids. Anisic acid has been characterized as a classical non-competitive inhibitor of the oxidation of L-3, 4-dihydroxyphenylalanine (L-DOPA), and the hydroxylation of L-tyrosine catalyzed by tyrosinase (EC 1. 14. 18. 1). Additionally, anisic acid is a metabolite of aniracetam, a cognition enhancer.

ferulic acid derivatives

P-coumaric acid (PubChem CID: 637542) is also known as 4-hydroxycinnamic acid, a flavoring compound.

Ferulic acid (PubChem CID: 445858) trans-Ferulic acid is a highly abundant phenolic phytochemical  present in plant cell walls.  It is one of the most abundant phenolic acids in plants, varying from 5 g/kg in wheat bran to 9 g/kg in sugar-beet pulp and 50 g/kg in corn kernel. It occurs primarily in seeds and leaves, both in its free form (rarely) and covalently linked to lignin and other biopolymers.  Ferulic acid is  usually found as ester cross-links with polysaccharides in the cell wall, such as

• arabinoxylans in grasses
• pectin in spinach and sugar beet
• xyloglucans in bamboo
• cross-link with proteins

Due to its phenolic nucleus and an extended side chain conjugation (carbohydrates and proteins), it readily forms a resonance stabilized phenoxy radical which accounts for its potent antioxidant potential.

This could be an interesting consideration in comparing use of pecan flour versus pecan tea in the diet.

Sinapaldehyde (PubChem CID: 5280802) is listed a food additive that may appear in wines by way of fermentation in oak barrows.  It may also be an inhibitor of cyclooxygenases.  Clyclooxygenases produce prostaglandins, mediators of inflammation.

Resveratrol (PubChem CID: 445154)  is a phytoalexin derived from grapes and other food products with antioxidant and potential chemopreventive activities. Resveratrol induces phase II drug-metabolizing enzymes (anti-initiation activity); mediates anti-inflammatory effects, and inhibits cyclooxygenase.

Rosmarinic acid (PubChem CID: 5281792)  is an ester of caffeic acid and 3, 4-dihydroxyphenyllactic acid.   Rosmarinic acid is one of the polyphenolic substances contained in culinary herbs such as perilla (Perilla frutescens L. ), rosemary (Rosmarinus officinalis L. ), sage (Salvia officinalis L. ), mint (Mentha arvense L. ), and basil (Ocimum basilicum L. ). A recent report in PubMed documents rosmarinic acid protecting cerebral granular neurons from nitrosative stress and  glutamate/glycine excitotoxicity.

Glycosides

Apigenin (PubChem CID: 5280443). aka cosmosiin,  is a member of the class of compounds known as flavonoid-7-O-glycosides. Cosmosiine can be found in a number of food items, such as  thyme, white lupine, oregano, and orange mint. Cosmosiin can also be found in dandelion coffee. Cosmosiin can also be found plants such as wild celery and anise. Cosmosiin has been shown to exhibit anti-platelet function

Chlorogenic acid (PubChem CID: 1794427)  Chlorogenic acid is an ester of caffeic acid and quinic acid. Chlorogenic acid is the major polyphenolic compound in coffee, isolated from the leaves and fruits of dicotyledonous plants. This compound, long known as an antioxidant, also slows the release of glucose into the bloodstream after a meal.

Quercetin derivatives

Taxifolin (PubChem CID: 439533)  Wikipedia lists taxifolin as a general flavanoid in vegetables, fruits, tea wine and cocoa, and milk thistle.

Fustin (PubChem CID: 5317435)… PubChem has very little information on this compound. Wikipedia lists fustin as a component of young fustic and  lacquer trees.

Quercitin (PubChem CID: 5280343) is a flavonoid widely distributed in many plants and fruits including red grapes, citrus fruit, tomato, broccoli, leafy green vegetables, and a number of berries, including raspberries and cranberries. Quercetin, ubiquitous in plant food sources and a major bioflavonoid in the human diet. it may produce antiproliferative effects resulting from the modulation of either EGFR or estrogen-receptor mediated signal transduction pathways.  Quercetin also produces anti-inflammatory and anti-allergy effects mediated through the inhibition of the lipoxygenase and cyclooxygenase pathways, thereby preventing the production of pro-inflammatory mediators.

Eriodictyol (PubChem CID: 440735) is, according to PubChem, safe at current levels used as a flavoring agent.  Eriodictyol, a bitter reducing agent used in the wine industry, is being explored as a UV filter for sun screens PubMed.

Galangin (PubChem CID: 16131409)is found in the roots of plants in the ginger family.  In another recent PubMed report a Chinese group the explored the use o galangin in reducing hepatic reperfusion injury.  Use in traditional Asian medicine was cited in this report.

Myricetin (PubChem CID: 5281672) is  a naturally-occurring flavonoid found in many grapes, berries, fruits, vegetables, herbs, as well as other plants. Walnuts are a rich dietary source (PubChem via Wikipedia).  Wikipedia also describes the potential of myricetin of being a pro-oxidant in the presence of copper and iron.   A recent Columbian report in PubMed examined the ability of nyricetin to inhibit a protease from a local pit viper of the Bothrops genus.

Naringerin (PubChem CID: 42607905) is poorly described in PubChem.  Unlike the other members of this group, naringerin is glycosylated and is missing a hydroxyl group on one of the aromatic rings.  A very recent PubMed reports that this common food component narigerin in bread prevents advanced glycation end products and acrylamide formation in the bread crust.  Wikipedia lists grapefruit as a good source of this compound, which is being investigated as  a treatment of Alzheimer’s Disease.

Catechin related compounds

(-)-Catechin (PubChem CID: 73160) is found in cotton seed and woody plants.  Catechin is a tannin peculiar to green and white tea.  In black tea the roasting process reduces catechin. Catechin is a powerful, water soluble polyphenol and antioxidant that is easily oxidized. Several thousand types are available in the plant world.

Epicatechin (PubChem CID: 72276) is an antioxidant flavonoid, occurring especially in woody plants as both (+)-catechin and (-)-epicatechin (cis) forms.  A recent PubMed report suggests that foods rich in epicatechin might help manage type 2 diabetes.  This report lists cocoa, tea, grapes, apples, and berries as being a good food source of (-)epicatechin.

Aromadendrin (PubChem CID: 122850) is isolated from Citrus species and many other plants.   A very recent PubMed suggests that aromadendrin may be a suitable treatment for pressure overload cardiac hypertrophy.

Epicatechin gallate (PubChem CID: 107905) is an antioxidant found in green tea, grapes, and rhubarb.

Epigallocatechin (PubChem CID: 72277) is found in almond. (-)-Epigallocatechin is widespread in plants; broad beans are an especially good source; present in green and black tea.

Uncategorized polyphenols

Ellagic acid (PubChem CID: 5281855) is bound in pomegranates; and other plant foods. It is often regarded as an antioxidant.  The presence of ellagic acid also promotes the formation of color in red wines.  PubMed.

4-methylumbelliferone CID: 5280567) only a few plant science papers on PubChem.  It’s use is being explored as a hyaluron synthesis inhibitor and cancer treatment.  The dietary supplement 4-MU is being billed as a cancer fighting small molecule by some.

Thoughts for pecan tea

The gram amount of pecan flour used to brew pecan tea are kept within the safe range established by the Burdock Group study.

Some of the components of the aqueous/ethanol extract of pecans are pro-oxidants in the presence of copper and iron.  Testing for these and other heavy metals should be required for pecan flour used to make tea.  The Burdock batch was tested for heay metals and proven to be safe.

ESI-MS/MS mass spectrometry analysis of the aqueous extract of local pecan flour (Hillig 2018)  could prove valuable for the customer.  Though many components of pecan shells are being explored for medicinal attributes, health related claims should be avoided.  Achieving the therapeutic concentration one component would seem to be next to impossible.

A blood biomarker of oxidative stress  (Reckziegel 2011) is a nice way of showing some benefit of a drink that should not be consumed to treat a specific disease condition.

References

Dolan L et al. Toxicol Rep. (2016) Safety studies conducted on pecan shell fiber, a food ingredient produced from ground pecan shells.Toxicol Rep.3:87-97.

Hilbig J, Alves VR, Müller CMO, Micke GA, Vitali L, Pedrosa RC, Block JM. (2018)Ultrasonic-assisted extraction combined with sample preparation and analysis using LC-ESI-MS/MS allowed the identification of 24 new phenolic compounds in pecan nut shell [Carya illinoinensis (Wangenh) C. Koch] extracts. Food Res Int. 106:549-557.

Porto LC, da Silva J, Sousa K, Ambrozio ML, de Almeida A, Dos Santos CE, Dias JF, Allgayer MC, Dos Santos MS, Pereira P, Ferraz AB, Picada JN. (2016) Evaluation of Toxicological Effects of an Aqueous Extract of Shells from the Pecan Nut Carya illinoinensis (Wangenh.) K. Koch and the Possible Association with Its Inorganic Constituents and Major Phenolic Compounds. Evid Based Complement Alternat Med. 2016;2016:4647830

Reckziegel P, Boufleur N, Barcelos RC, Benvegnú DM, Pase CS, Muller LG, Teixeira AM, Zanella R, Prado AC, Fett R, Block JM, Burger ME.(2011) Oxidative stress and anxiety-like symptoms related to withdrawal of passive cigarette smoke in mice: beneficial effects of pecan nut shells extract, a by-product of the nut industry. Ecotoxicol Environ Saf. 74(6):1770-8.