Effects of hot water extract of Curcuma longa on human epidermal keratinocytes in vitro and skin conditions in healthy participants: A randomized, double‐blind, placebo‐controlled trial

Summary

Background

Curcuma longa has been reported to have anti‐inflammatory effects. Skin inflammation impairs skin functions.

Objectives

Our aim was to investigate the effect of a hot water extract of C longa (WEC) on skin conditions in cell studies using keratinocytes and in clinical trials.

Methods

We measured proinflammatory cytokine levels in ultraviolet B‐irradiated keratinocytes in the presence or absence of WEC. The effects of WEC on hyaluronan production in keratinocytes were also determined. In a randomized, double‐blind, placebo‐controlled trial, 47 healthy participants were assigned to 8‐week intervention groups with daily intakes of WEC with or without curcumin or a placebo. The water content and transepidermal water loss in the face and minimal erythema dose on the back after ultraviolet B irradiation were evaluated every 4 weeks.

Results

Hot water extract of C longa significantly inhibited increases in ultraviolet B‐induced tumor necrosis factor α and interleukin 1β at the mRNA and protein levels. WEC also significantly increased hyaluronan production from nonstimulated keratinocytes. In the randomized, double‐blind, placebo‐controlled trial, increases from baseline in the water content of the face were significantly greater at weeks 4 and 8 in the WEC group, but not in the WEC + curcumin group, than in the placebo group. There were no significant differences in transepidermal water loss and minimal erythema dose among the groups.

Conclusions

The cell studies confirmed that WEC has anti‐inflammatory effects and augments hyaluronan production in the skin. The results of clinical trials suggest that WEC may be useful for moisturizing facial skin.

Trial registration

UMIN Clinical Trials Registry 000028510. Retrospectively registered.

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