In this study, we observed that PIC stimulated hyaluronic acid biosynthesis in human skin fibroblasts by upregulating HAS2 expression and downregulating HYAL2 expression. Furthermore, the induction of HAS2 by PIC was impeded by a SIRT inhibitor, suggesting that PIC enhances HAS2 expression via increased SIRT1 expression. Previous clinical trials have demonstrated that PIC intake enhances skin moisture and elasticity [[15], [16], [17]], and our findings suggest that the upregulation of hyaluronic acid biosynthesis by PIC contributes to these improvements in skin function. Notably, PIC has been reported to induce HAS2 mRNA expression in mouse fibroblasts [29], and our study reveals that PIC also suppresses hyaluronic acid degradation, shedding light on the mechanisms underlying its effects on human skin.
PIC has been demonstrated to enhance SIRT1 activity [20] and elevate SIRT1 levels in human monocytic leukemia cell lines [32]. In an in vivo study, mice fed a high-fat diet and orally administered PIC (10 mg/kg/day) for four weeks exhibited increased expression of SIRT1, SIRT3, and SIRT6 in the liver than the high-fat diet group [21]. While there have been no previous reports on the effects of PIC on SIRT1 in skin fibroblasts, our study revealed that PIC also induces SIRT1 in human skin fibroblasts. This induction suggests that PIC may exert beneficial effects on skin through the upregulation of SIRT1.
Additionally, the reduction in HYAL2 expression induced by PIC was not reversed by SIRT1 inhibition, suggesting that SIRT1 may not be directly involved in hyaluronic acid degradation. Recently, the involvement of a long noncoding RNA, HA synthase 2 antisense 1 (HAS2-AS1), has been shown as a new mechanism of action for the regulation of HAS2 gene expression [35].

Piceatannol is a tetrahydric polyphenol and an analogue form of resveratrol. The content of piceatannol in freeze-dried passion fruit seed was 4.8 mg/g when extracted using 70% acetone, which translates into 2.2 mg/g of raw material.
Our results showed that passion fruit contains a very high content of piceatannol in a natural state, which is nearly 50 times larger than that found in grapes (described above). Here, we report for the first time that piceatannol is present in passion fruit seed and that this content of piceatannol is much higher than that known for any other plants. Piceatannol was not detected in the rind or pulp of passion fruit.
Both piceatannol and resveratrol increased soluble collagen in SF-TY cells; piceatannol increased soluble collagen significantly at 5 μM, whereas resveratrol increased soluble collagen significantly at 10 μM.
Piceatannol has been reported to have a wide variety of effects on the skin, including promoting collagen production, inhibiting melanin synthesis, inducing the antioxidant glutathione, and eliminating reactive oxygen species. In this study, a randomized, placebo-controlled, double-blind trial was conducted to clinically evaluate the effects of piceatannol-rich passion fruit seed extract on the skin of healthy Japanese women (age, 35-54 y). Thirty-two women with dry skin received either passion fruit seed extract (5 mg piceatannol) or a placebo (dextrin) for 8 wk. Skin hydration and other parameters on the face were assessed at 0, 4, and 8 wk by using specialized equipment. Furthermore, questionnaire interviews were conducted regarding the physical condition of subjects at 0, 4, and 8 wk. The results showed that consumption of passion fruit seed extract led to significant increases in the moisture content of human skin after 4 and 8 wk compared with that before the trial. The amount of transepidermal water loss decreased over time, although the differences were not significant. Moreover, a stratified analysis of subjects with moisture values of ≤200 μS revealed increased moisture content in the passion fruit seed extract group as compared with the placebo group. Furthermore, the results of questionnaires showed significant reductions in “perspiration” and “fatigue” in the passion fruit seed extract group as compared with the placebo group. These results indicate that oral intake of passion fruit seed extract that is rich in piceatannol could improve the moisture of dry skin and reduce fatigue.
Objectives: The aim of this study was to investigate the effect of a dietary supplement containing piceatannol on skin in healthy subjects with dry skin. Methods: A randomized, double blind, placebo-controlled parallel-group, comparison study was conducted in 36 healthy subjects (30-60 years old) with dry skin. They were randomly divided into two groups and ingested either the test product (125 mL drink containing 10 mg piceatannol derived from passion fruit seed extract) or the control product (placebo drink) three packs per day for 8 weeks. The outcomes about skin condition were evaluated using moisture content of horny layer, Trans-epidermal Water Loss (TEWL) and viscoelasticity of the face. This study was registered in UMIN-CTR (UMIN000030491). Results: The water content and elastic recovery from the pretrial were significantly increased at 8 week in the test product containing piceatannol compared to the placebo group. Conclusions: These result suggested that the daily supplementation of piceatannol derived from passion fruit seed extract is effective for skin moisture.
https://www.researchgate.net/publication/327619061_Effects_of_oral_intake_of_piceatannol_on_skin_moisture_-_A_randomized_double-blind_placebo-controlled_parallel-group_comparison_study