Researchers in Germany and the United States evaluated the effectiveness of a proprietary plant-based blend (PB-Blend)—formulated from seven ingredients and standardized for polyphenols, catechins and curcuminoids—in modulating multiple reactive oxygen species (ROS) linked to a weakened immune response.
The research was funded by VDF FutureCeuticals, Inc., the supplier of PB-Blend, and several of the researchers involved were employed by the company.
Modulating immune response
Respiratory viruses can trigger excessive production of ROS and reduce levels of bioavailable nitric oxide (NOHb), which can disrupt immune balance and lead to the release of inflammatory cytokines and chemokines.
Studies have found that viruses such as influenza, rhinovirus, RSV and COVD-19 cause excessive cytokine production, apoptosis in lung and vascular cells, and redox imbalances—shared mechanisms that suggest a common pattern in ROS overproduction and immune dysregulation.
Key enzymes such as NOX2 and iNOS are central regulators of these immune responses, and therefore, the researchers suggest that suppressing their activity may help reduce symptoms.
They hypothesized that the targeted PB-Blend could modulate these immune responses, with previous research finding that a 29-ingredient iteration of the blend reduced ROS and boosted NOHb levels.
Study details
The randomized, double-blind, single-dose clinical trial included 28 German participants (13 males and 15 females) who had recently recovered from moderate COVID-19.
At baseline, participants showed normal blood pressure, heart rate, and oxygen levels. However, they presented moderately elevated fasting glucose and LDL-cholesterol, slight reductions in flow-mediated dilation (FMD) and forced vital capacity (FVC), and over 85% reported fatigue and strength loss. PCR testing confirmed previous COVID-19 infections, with moderate levels of Cov-2-IgG and IgM antibodies.
Subjects were assigned to receive either a 50 mg encapsulated dose of PB-Blend or 1,000 mg of vitamin C as a control. Following administration, the researchers measured bioavailable nitric oxide (NO) levels (via NOHb) and markers of ROS at baseline and at 30, 60, 120 and 180 minutes post-dose.
The supplement blend included extracts derived from blueberry, broccoli, cherry, green coffee bean, green tea, kale and turmeric, combined in proprietary ratios and standardized to a minimum of 60% total polyphenols, 30% catechins and 3% curcuminoids.
At intake, participants exhibited extremely high cellular metabolic activity (CMA), indicating activated inflammatory defenses, elevated ROS production (particularly from NOX2) and mitochondrial dysfunction.
After administering a single oral dose of 50 mg PB-Blend or 1,000 mg Vit C, the researchers found that the PB-Blend significantly reduced ROS generation from mitochondria, iNOS and NOX2 after two hours, indicating broad antioxidant and anti-inflammatory activity. Vitamin C ingestion in comparison showed a weaker and shorter-lived effect, primarily reducing NOX2-derived ROS without significantly impacting mitochondrial or iNOS pathways.
The PB-Blend was also found to increase hemoglobin-bound NOHb levels, which the authors noted indicated improved endothelial function and restoration of NO bioavailability. Vitamin C however had no significant effect on NOHb.
“This is the first study showing real-time elevations in the iNOS and NOX2 enzymatic systems in a population recovering from a moderate course of COVID-19,” the researchers wrote.
“Results suggest that 50 mg of PB-Blend, a plant-based dietary supplement that exhibits a broad spectrum of antioxidant activities, has potential to modulate the therapeutic targets that can become disbalanced due to viral infection.”
They added that further research should be placebo-controlled, include a higher number of participants and examine the impact of both the acute and long-term supplementation with PB-Blend.
Source: Int. J. Mol. Sci. 2025, 26(11), 5209. doi: 10.3390/ijms26115209. “A Plant-Based Dietary Supplement Exhibits Significant Effects on Markers of Oxidative Stress, Inflammation, and Immune Response in Subjects Recovering from Respiratory Viral Infection: A Randomized, Double-Blind Clinical Study Using Vitamin C as a Positive Control”. Authors: Fink, B. et al.