Methods Used for Enhancing the Bioavailability of Oral Curcumin in Randomized Controlled Trials: A Meta-Research Study

The effects of curcumin supplementation on biomarkers of inflammation, oxidative stress, and endothelial function: A meta-analysis of meta-analyses

Numerous interventional studies have revealed the beneficial impact of curcumin supplementation on inflammation, oxidative stress, and endothelial function biomarkers, but the findings are still inconsistent. Thus, this study was conducted to investigate the effects of curcumin supplementation on inflammation, oxidative stress, and endothelial function biomarkers. A meta-analyses of randomized clinical trials was performed by searching PubMed, Embase, Scopus, and Web of Science up to March 31, 2024. Pooled estimates of 21 meta-analyses revealed that curcumin significantly reduced CRP (weighted mean difference (WMD) = -0.87; 95 % CI: - 1.14, - 0.59, P< 0.001), tumor-necrosis factor-alpha (TNF-α) (WMD = -2.72; 95 % CI: -4.05, -1.38; P< 0.001), interleukin-6 (IL-6) (WMD = -0.97, 95 % CI: -1.40, -0.54; P< 0.001), malondialdehyde (MDA) (Effect size (ES) = -0.81; 95 % CI: -1.39, -0.23, P = 0.006) and pulse wave velocity (PWV) (WMD = -45.60; 95 % CI: -88.16, -3.04, P = 0.036), and increased flow-mediated dilation (FMD) (WMD = 1.64, 95 % CI: 1.06, 2.22, P < 0.001), catalase (CAT) (WMD = 10.26; 95 % CI: 0.92, 19.61, P= 0.03), glutathione peroxidase (GPx) (WMD = 8.90; 95 % CI: 6.62, 11.19, P <0.001), and superoxide dismutase (SOD) levels (WMD = 20.51; 95 % CI: 7.35, 33.67, P= 0.002 and SMD = 0.82; 95 % CI: 0.27, 1.38, P= 0.004). However, curcumin did not significantly change total antioxidant capacity (TAC) (ES = 0.29; 95 % CI: -0.09, 0.66, P= 0.059). These results suggest that curcumin has a beneficial effect on CRP, IL-6, TNF-α, SOD, GPx, CAT, MDA, PWV, and FMD levels and may be an effective adjunctive therapy for improving inflammation, oxidative stress, and endothelial function. Registration number: PROSPERO, CRD42024539018.

Analgesic Potential Comparison Between Piperine-Combined Curcumin Patch and Non-Piperine Curcumin Patch: A Pragmatic Trial on Post-Cleft Lip/Palate Surgery Pediatric Patients

Purpose

Despite its well-acknowledged analgesic potential, curcumin's low bioavailability has been recognized. Piperine, a substance naturally contained in pepper, has been known for its effect on increasing curcumin bioavailability. To investigate the analgesic potential of curcumin and piperine addition to curcumin patch used as adjuvant therapy in the management of acute postoperative orofacial pain.

Patients and Methods

This pragmatic trial recruited 75 patients that underwent oromaxillofacial surgery at Unpad Dental Hospital, Bandung, Indonesia. Research participants were randomly assigned to three different groups: the first group that did not receive any intervention other than the post-operative standard treatment (POST), the second group that received POST and non-piperine curcumin patch, and the third group that received POST and piperine-combined curcumin patch. Participants' pain intensity was evaluated by using the face, leg, activity, cry, and consolability (FLACC) pain scale and salivary prostaglandin-E2 (PGE2) level for two-time points, which were eight hours apart. All data were gathered and analyzed to compare the within and between-group differences.

Results

Within groups comparison of the FLACC scores for two evaluation points showed significant differences for all groups (p < 0.01). For salivary PGE2 analysis, a comparison of the non-piperine group to the piperine group also showed significant results. Yet, when all three groups were compared, regardless of the differences, the results were not statistically significant.

Conclusion

Despite of the proven efficacy of curcumin patch, the addition of piperine to the curcumin patch in the current study did not provide any significant effects. Further investigation is of importance.

Curcumin as a Multifunctional Spice Ingredient against Mental Disorders in Humans: Current Clinical Studies and Bioavailability Concerns

BACKGROUND

Mental disorders in terms of depression, anxiety, and stress are one of the major causes of burden globally. Over the last two decades, the use of plant-based substances in the treatment of mental disorders in combination or not with medication has increasingly attracted the interest of the scientific research community. However, even if there is a plethora of naturally occurring bioactive compounds, most of them have low bioavailability, rendering them unable to insert into the bloodstream to exert their biological activities.

METHODS

This is a comprehensive narrative review that critically summarizes and scrutinizes the new approaches to the treatment of mental disorders using curcumin, also highlighting its bioavailability properties. The most accurate were searched using effective and relevant keywords.

RESULTS

This narrative review reveals substantial evidence that curcumin can exert significant effects on several mental disorders. However, despite the low cost, the extensive and confirmed potency of curcumin and its involvement in signaling pathways and the scientifically confirmed data regarding its molecular mechanisms of action against mental disorders, this naturally occurring compound presents low oral bioavailability. Pharmaceutical technology has provided solutions to increase the bioavailability of curcumin. Combination with piperine, galactomannosides, liposomal formulation or nanoformulation overcomes the bioavailability and solubility disadvantages.

CONCLUSIONS

Although curcumin demonstrates anti-anxiety, anti-depressive and anti-stress properties, studies on humans are limited and heterogeneous. Further research is highly recommended to determine the most functional formula, dose, duration, and possible side effects of curcumin on mental disorders in humans. Based on the current knowledge, the curcumin nanoformulation and Theracurmin, a form of colloidal submicroscopic particles, seem to be the most effective bioavailable formulations, which may be examined in future clinical human studies.

The effect of curcumin supplementation on circulating adiponectin and leptin concentration in adults: a GRADE-assessed systematic review and meta-analysis of randomised controlled trials

Curcumin is a phytocompound found in the root of turmeric, a common herbal ingredient in many Asian cuisines. The compound contains anti-inflammatory activity, which is mediated through an upregulation of adiponectin and reduction of leptin. Results of randomised controlled trials (RCT) have shown that the effects of curcumin on adipokines are conflicting. Therefore, the current systematic review and meta-analysis of RCT were conducted with the aim of elucidating the role of curcumin supplementation on serum adiponectin and leptin. The search included PubMed, Embase, Cochrane Library, Scopus, Web of Science and Google Scholar from inception to August 2023. For net changes in adipokines, standardised mean differences (SMD) were calculated using random effects models. Thirteen RCT with fourteen treatment arms were eligible for inclusion in this meta-analysis. Curcumin supplementation was effective in increasing serum adiponectin (SMD = 0·86, 95 % CI (0·33, 1·39), P < 0·001; I2 = 93·1 %, P < 0·001) and reducing serum leptin (SMD = -1·42, 95 % CI (-2·29, -0·54), P < 0·001; I2 = 94·7 %, P < 0·001). In conclusion, curcumin supplementation significantly increased circulating adiponectin and decreased leptin levels in adults.

Green Cancer Prevention and Beyond

The concept of green chemoprevention was introduced in 2012 by Drs. Jed Fahey and Thomas Kensler as whole-plant foods and/or extract-based interventions demonstrating cancer prevention activity. Refining concepts and research demonstrating proof-of-principle approaches are highlighted within this review. Early approaches included extensively investigated whole foods, including broccoli sprouts and black raspberries showing dose-responsive effects across a range of activities in both animals and humans with minimal or no apparent toxicity. A recent randomized crossover trial evaluating the detoxification of tobacco carcinogens by a broccoli seed and sprout extract in the high-risk cohort of current smokers highlights the use of a dietary supplement as a potential next-generation green chemoprevention or green cancer prevention approach. Challenges are addressed, including the selection of dose, duration and mode of delivery, choice of control group, and standardization of the plant food or extract. Identification and characterization of molecular targets and careful selection of high-risk cohorts for study are additional important considerations when designing studies. Goals for precision green cancer prevention include acquiring robust evidence from carefully controlled human studies linking plant foods, extracts, and compounds to modulation of targets for cancer risk reduction in individual cancer types.

Bioavailability of Oral Curcumin in Systematic Reviews: A Methodological Study

Curcumin is a natural compound found in turmeric that exhibits diverse biological activities. However, its poor bioavailability limits its therapeutic application, which has led to the development of various bioavailability-improved formulations. In this methodological study, we analyzed whether systematic reviews on curcumin considered the bioavailability of systemic oral curcumin formulations when synthesizing evidence from human clinical trials. A total of 171 systematic reviews published between 2003 and 2022 were included in the study. From the included studies, we extracted data on study characteristics; type of curcumin; methods; and reporting regarding bioavailability, funding, and conflict of interest. Our results show that systematic reviews rarely consider the variable bioavailability of tested curcumin formulations. Relevant statistical subgroup and/or sensitivity analyses were reported in the methods and results of only 3.5% and 6.4% of reviews, respectively. However, more reviews mentioned bioavailability in their discussion (57%) or conclusion (13%). The detailed analysis of the included systematic reviews suggests that there is broad recognition of product bioavailability as a crucial factor affecting the health effects of curcumin, which is not accompanied by adequate evidence synthesis. Therefore, the results of most systematic reviews on orally administered curcumin should be taken with caution.

Overview of Curcumin and Piperine Effects on Glucose Metabolism: The Case of an Insulinoma Patient’s Loss of Consciousness

The hypoglycemic properties of curcumin supplements in therapeutic doses are well-known and may represent a useful tool for the treatment of chronic diseases such as metabolic syndrome, insulin resistance and type 2 diabetes. The poor bioavailability of curcumin can be improved with the concomitant administration of piperine, with no severe adverse effects on glycemia reported so far in the literature. In this article, we further discuss a previously reported case of a helicopter pilot, affected by grade I obesity who, under curcumin and piperine treatment, experienced a transient loss of consciousness (TLOC), during a low-altitude flight. This episode led to a diagnosis of insulinoma, previously asymptomatic. We hypothesized that the combined effects of curcumin and piperine might have caused a severe hypoglycemic episode and subsequent TLOC. Therefore, further studies should be conducted to evaluate the safety of curcumin and piperine supplementation in subjects with impaired glucose metabolism and insulin secretion.

Effects of Particle Size of Curcumin Solid Dispersions on Bioavailability and Anti-Inflammatory Activities

The delivery of curcumin (CUR) using the solid dispersion system (CUR solid dispersions; C-SDs) has been shown to improve CUR bioavailability. However, it is unclear how different particle sizes of C-SDs affect the bioavailability and biological activities of CUR. Hence, we prepared C-SDs in different sizes using food-grade excipients and evaluated their bioavailability and biological activities. By pulverizing large particle sizes of C-SDs using zirconia beads, we successfully prepared C-SDs I-IV (particle size: (I) 120, (II) 447, (III) 987, (IV) 1910 nm). When administrated orally in rats, the bioavailability of CUR was increased with decreasing C-SDs size, most likely by improving its solubility in micelles. When administrated intravenously in rats, blood concentrations of CUR were increased with increasing particle size, suggesting that larger C-SDs presumably control the metabolic conversion of CUR. In RAW264 cells, more CUR was taken up by cells as their sizes reduced, and the more potent their anti-inflammatory activities were, suggesting that smaller C-SDs were taken up through a number of cellular uptake pathways. Altogether, the present study showed an evident effect of C-SDs size on their bioavailability and anti-inflammatory activities—information that serves as a basis for improving the functionality of CUR.

Nanoparticles Based on Chondroitin Sulfate from Tuna Heads and Chitooligosaccharides for Enhanced Water Solubility and Sustained Release of Curcumin

This study aimed to separate chondroitin sulfate (CS) from the heads of skipjack tuna (Katsuwonus pelamis) and yellowfin tuna (Thunnus albacares), by-products derived from canned tuna processing, via a biological process. The use of 1% w/w papain and an incubation time of 48 h resulted in a degree of hydrolysis of 93.75 ± 2.94% and a CS content of 59.53 ± 1.77 mg/100 g. The FTIR spectra of extracted CS products exhibited identical functional groups found in commercially available CS. The molecular weights of CS extracted from skipjack and yellowfin tuna heads were 11.0 kDa and 7.7 kDa, respectively. Subsequently, a CH:CS ratio of 3:2 for CS and chitooligosaccharides (CH) was chosen as the optimal ratio for the preparation of spherical nanoparticles, with %EE, mean particle size, PDI, and zeta potential values of 50.89 ± 0.66%, 128.90 ± 3.29 nm, 0.27 ± 0.04, and -12.47 ± 2.06, respectively. The CU content was enhanced to 127.21 ± 1.66 μg/mL. The release of CU from this particular nanosystem involved mainly a drug diffusion mechanism, with a burst release in the first 3 h followed by a sustained release of CU over 24 h. The DPPH and ABTS scavenging activity results confirmed the efficient encapsulation of CU into CHCS nanoparticles. This study will provide a theoretical basis for CS derived from tuna head cartilages to be used as a functional component with specific functional properties in food and biomedical applications.