Green Potatoes, Solanine, Sulfa Drugs, and Glucose-6-Phosphate Dehydrogenase (G6PD) Deficiency

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A Personal Experience That Raised Genetic Questions

Sixty years ago, I experienced a frightening medical episode that has remained with me ever since. After exposure to sulfa compounds and consuming potatoes treated with sulfites (Schwefel in German) preservatives commonly used at the time to prevent peeled potatoes from discoloring, I lost consciousness. Growing up in post-war Germany, I was also familiar with concerns about solanine, a natural toxin concentrated in potato skins, sprouts, and green tissues. Having lived through years of food shortages, many older Germans were careful to peel potatoes thoroughly to reduce the risk of poisoning from green or sprouted potatoes.

That incident led me to wonder whether my unusual sensitivities to sulfites, alcohol, sulfa drugs, phosphorus-containing compounds, and other chemicals might have a biological or genetic basis. Over time, I became interested in the genetic and biochemical pathways that influence how the body detoxifies reactive compounds and responds to environmental exposures.

Why Do Some People React Strongly to Sulfa Drugs?

Sulfa drugs, or sulfonamide medications, are widely used antibiotics and therapeutic agents. Most people tolerate them well, but some individuals develop severe reactions. These reactions may arise from immune mechanisms, genetic predisposition, or metabolic differences.

Immune Hypersensitivity

The most common cause of adverse reactions to sulfa drugs is an immune-mediated hypersensitivity response. After administration, the liver metabolizes sulfonamides into reactive compounds such as hydroxylamine metabolites. These metabolites can bind to proteins within the body, forming complexes that the immune system may mistakenly identify as foreign.

The resulting immune response may involve antibodies or T cells and can range from mild skin rashes to life-threatening conditions such as Stevens–Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN). 

It is currently no widely accepted evidence that:

  1. G6PD deficiency causes SJS through NO deficiency, or
  2. Impaired NO-mediated vasodilation is a major driver of SJS pathology.

Epigenetic Aspect: 

While the root G6PD deficiency is genetic, emerging research shows G6PD-derived NADPH influences epigenetic processes, such as DNA methylation and gene expression, to help cells adapt to hypoxic or oxidative stress. https://pmc.ncbi.nlm.nih.gov/articles/PMC7191486/ 

Genetic Predisposition

Research has shown that certain genetic variants, particularly within the human leukocyte antigen (HLA) system, increase susceptibility to severe drug reactions. Individuals carrying specific HLA alleles may be more likely to develop serious immune responses when exposed to particular medications.

Metabolic Enzyme Deficiencies

Not all reactions are allergic. Some result from inherited metabolic differences that impair the body's ability to neutralize oxidative stress. One of the best-known examples is glucose-6-phosphate dehydrogenase (G6PD) deficiency.

What Is G6PD?

Glucose-6-phosphate dehydrogenase (G6PD) is an enzyme present in nearly all cells but is particularly important in red blood cells. Its primary role is to generate NADPH, a molecule that protects cells against oxidative damage.

The reaction catalyzed by G6PD is:

Glucose-6-phosphate + NADP⁺ → 6-phosphogluconolactone + NADPH + H⁺

Neither glucose-6-phosphate nor NADP⁺ is genetic or epigenetic in nature. Rather, they are metabolic molecules that function as the substrate and coenzyme required for G6PD activity.

This reaction represents the first and rate-limiting step of the pentose phosphate pathway, a major cellular pathway responsible for producing NADPH.

The Importance of NADPH

NADPH serves as one of the cell's primary sources of reducing power. It supports numerous biological functions, including:

  • Protection against oxidative stress
  • Regeneration of glutathione and other antioxidants
  • Fatty acid synthesis
  • Cholesterol production
  • Nucleotide synthesis
  • Detoxification reactions

Red blood cells are especially dependent on G6PD because they lack alternative mechanisms for generating sufficient NADPH. When G6PD activity is reduced, red blood cells become vulnerable to oxidative injury and premature destruction.

Sources of NADPH Production

Pentose Phosphate Pathway

In humans and most non-photosynthetic organisms, the pentose phosphate pathway is the primary source of NADPH. G6PD initiates this pathway by transferring electrons from glucose-6-phosphate to NADP⁺.

Alternative Metabolic Pathways

Additional sources of NADPH include:

  • Malic enzyme
  • NADP⁺-dependent isocitrate dehydrogenases (IDH1 and IDH2)
  • Folate-mediated one-carbon metabolism

Together, these pathways help maintain cellular redox balance and support antioxidant defenses.

A redox (oxidation-reduction) reaction is a chemical process where electrons are transferred between two substances. 

G6PD Deficiency and Hemolytic Anemia

G6PD deficiency is one of the most common inherited enzyme deficiencies worldwide. It is inherited as an X-linked trait and therefore affects males more frequently than females.

Because G6PD-deficient red blood cells cannot adequately neutralize oxidative stress, exposure to certain triggers can lead to acute hemolytic anemia, a condition in which red blood cells are destroyed faster than the body can replace them.

Common triggers include:

  • Sulfonamide antibiotics
  • Certain antimalarial medications
  • Fava beans (favism)
  • Naphthalene-containing mothballs
  • Severe bacterial or viral infections
  • Other oxidizing chemicals

Symptoms typically appear within 24 to 72 hours after exposure and may include:

  • Jaundice
  • Dark or tea-colored urine
  • Fatigue
  • Pallor
  • Rapid heartbeat
  • Shortness of breath
  • Weakness

Most episodes resolve once the triggering factor is removed, although severe cases may require hospitalization, intravenous fluids, or blood transfusions.

What Is Solanine?

Solanine is a naturally occurring glycoalkaloid toxin produced by plants in the nightshade family.

It is found primarily in:

  • Potatoes, especially green or sprouted potatoes
  • Eggplants
  • Tomatoes, particularly unripe fruit

Potatoes exposed to light produce chlorophyll, causing them to turn green. While chlorophyll itself is harmless, its presence often indicates elevated glycoalkaloid levels, including solanine.

High levels of solanine can cause:

  • Nausea
  • Vomiting
  • Abdominal pain
  • Diarrhea
  • Headaches
  • Dizziness
  • Neurological symptoms in severe cases

Solanine and G6PD Deficiency: Is There a Connection?

Although solanine and G6PD deficiency involve different biological mechanisms, they intersect through oxidative stress.

Current scientific evidence does not identify solanine as a major trigger of G6PD-related hemolysis. Unlike fava beans or sulfonamide drugs, solanine is not recognized as a classic cause of hemolytic crises in G6PD-deficient individuals.

However, several observations suggest a theoretical connection:

  • Solanine can increase cellular stress and membrane damage.
  • G6PD-deficient cells are more susceptible to oxidative injury.
  • Excessive consumption of green or heavily sprouted potatoes may increase oxidative burden.

For these reasons, individuals with G6PD deficiency may wish to avoid potatoes that are green, bitter, or heavily sprouted, even though definitive evidence linking solanine to hemolytic crises remains limited.

Genetic Variants Associated with G6PD Deficiency

In my case, G6PD deficiency is caused by numerous variants within the G6PD gene on the X chromosome. Several well-characterized variants include:

Variant        rs ID
G6PD A− (Val68Met)            rs1050828
G6PD A (Asn126Asp)                rs1050829
G6PD Mediterranean (Ser188Phe)            rs5030868
G6PD Canton            rs72554664
G6PD Kaiping            rs72554665

Among populations of African ancestry, rs1050828 is one of the most extensively studied variants and is strongly associated with G6PD deficiency when present within the appropriate genetic background.

My experience with sulfa compounds, sulfite-treated potatoes, and subsequent chemical sensitivities raised questions that continue to be relevant today. While it is impossible to determine retrospectively whether G6PD deficiency, sulfite sensitivity, immune hypersensitivity, solanine exposure, or another metabolic factor contributed to my reaction, the episode highlights the complex interplay between genetics, metabolism, environmental exposures, and human health.

G6PD is a critical protective enzyme that helps cells defend themselves against oxidative stress by generating NADPH through the pentose phosphate pathway. NADPH is essential not only for maintaining antioxidant defenses, particularly in red blood cells, but also for supporting numerous cellular processes involved in detoxification, biosynthesis, and vascular function. When G6PD activity is reduced, cells become more vulnerable to oxidative damage, increasing the risk of hemolytic anemia following exposure to certain drugs, infections, foods, or environmental chemicals.

Solanine, by contrast, is a naturally occurring glycoalkaloid toxin found in green, sprouted, or damaged potatoes. Although solanine is not recognized as a major trigger of G6PD-related hemolysis, excessive exposure may contribute to oxidative stress and cellular injury. Consequently, individuals with compromised antioxidant defenses may be more susceptible to its effects.

Emerging research also suggests that G6PD deficiency may affect vascular health through impaired nitric oxide (NO) production. Nitric oxide is a key signaling molecule that enables blood vessels to relax and dilate properly. Because the synthesis of nitric oxide depends on adequate NADPH availability, reduced G6PD activity may limit nitric oxide production, resulting in endothelial dysfunction and impaired vasodilation. This mechanism may contribute to circulatory abnormalities beyond the well-recognized effects of red blood cell damage.

Taken together, these observations illustrate how genetic variation can influence an individual's response to foods, medications, toxins, and environmental stressors. Understanding the relationships among G6PD activity, oxidative stress, detoxification pathways, nitric oxide metabolism, and environmental exposures provides valuable insight into why people differ in their susceptibility to adverse reactions and disease. Such knowledge reinforces the importance of personalized approaches to medicine, nutrition, and toxicology, particularly for individuals with inherited metabolic vulnerabilities

Reference:

Competitive oxidation of key pentose phosphate pathway enzymes modulates the fate of intermediates and NAPDH production https://www.sciencedirect.com/science/article/abs/pii/S0891584924005094

RecName: Full=Glucose-6-phosphate 1-dehydrogenase; Short=G6PD

https://www.ncbi.nlm.nih.gov/protein/P11413/

“Doctor, I have a Sulfa Allergy”: Clarifying the Myths of Cross-Reactivity
https://pmc.ncbi.nlm.nih.gov/articles/PMC6258578/

Allergic adverse reactions to sulfonamides
https://link.springer.com/article/10.1007/s11882-002-0033-y

Sulfa Allergy: Everything You Need to Know
https://www.verywellhealth.com/sulfa-drug-allergy-83067

Glucose-6-Phosphate Dehydrogenase Deficiency
https://www.ncbi.nlm.nih.gov/books/NBK470315/

RecName: Full=Glucose-6-phosphate 1-dehydrogenase; Short=G6PD
CDART Navigate results: https://www.ncbi.nlm.nih.gov/Structure/lexington/lexington.cgi?reqId=1101130900942576530&tdata=0

G6PD Deficiency Prevalence and Estimates of Affected Populations in Malaria Endemic Countries: A Geostatistical Model-Based Map
https://pmc.ncbi.nlm.nih.gov/articles/PMC7191486/

Glucose-6-Phosphate Dehydrogenase Deficiency
https://www.ncbi.nlm.nih.gov/books/NBK470315/

Anemia, nonspherocytic hemolytic, due to G6PD deficiency(CNSHA1)​
https://www.malacards.org/card/anemia_congenital_nonspherocytic_hemolytic_1

© 2000-2030 Sieglinde W. Alexander. All writings by Sieglinde W. Alexander have a five-year copyright. Library of Congress Card Number: LCN 00-192742 ISBN: 0-9703195-0-9 

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